Galileo in Rome
The Rise and Fall of a Troublesome Genius
William R. Shea and Mariano Artigas
ACKNOWLEDGEMENTS
We wish to thank most warmly the Templeton Foundation for providing us with a grant to coordinate our work and carry out research in the archives in Rome and Florence. We are also grateful to Paolo Galluzzi and his staff at the Institute and Museum of the History of Science in Florence, to Monsignor Alejandro Cifres, who has made the Archives of the Holy Office in the Vatican a friendly place to work, and to the officials of the Vatican Library, the Biblioteca di Archeologia e Storia dell’Arte and the Biblioteca Vallinceliana in Rome. We owe special thanks to Lucia Caravale of the Società Dante Alighieri in Rome for making available documents regarding the Palazzo Firenze, where Galileo spent a great part of his time in Rome, and to several others whom we are pleased to mention here: Corrado Calisi of the Biblioteca della Camera dei Deputati, who introduced us to the Galileo Rooms that were formerly part of the convent of Santa Maria sopra Minerva, where Galileo was tried; Irene Trevor of the American Academy in Rome, who graciously allowed us to visit the Casa Rustica, where Cesi’s dinner in honour of Galileo took place in 1611; Cosimo di Fazio, who provided information on the Florentine residences of Galileo and enabled us to visit the Convent of San Mateo in Arcetri; Mario Sirignano, of the Accademia dei Lincei who taught us to walk in Galileo’s footsteps in Rome; the librarians of the Biblioteca Nazionale and of the Archivio di Stato in Florence; Rafael Martinez of the Pontifical University of the Holy Cross in Rome, who undertook a detailed study of a manuscript on Galileo that contains novel and exciting material that one of us (Mariano) came across in the Archives of the Congregation for the Doctrine of the Faith in the Vatican (formerly the Holy Office). Special thanks to Eugenio Calimani, the Dean of the Faculty of Science of the University of Padua, for providing a friendly and stimulating environment in which to complete our book.
INTRODUCTION
Galileo is the father of modern science and a major figure in the history of mankind. He belongs to the small group of thinkers who transformed Western culture, and his clash with ecclesiastical authorities is one of the most dramatic incidents in the long history of the relations between science and religion.
In 1633 the Roman Inquisition condemned Galileo for teaching that the earth moves. The trial was the outcome of a series of events that are described in this book and are usually referred to as the Galileo Affair. It extended over a period of several years, during which different popes, cardinals, and civil personalities entered the scene and made their exit. We can even speak of two Galileo trials, one in 1616 and the other in 1633, although only the second was a trial in the legal sense. The new science, which today pervades our entire life, was just emerging, and very few were able to realize what was happening at the time. Most people were not ready to abandon cherished traditional ideas for daring hypotheses that had yet to be proved.
Galileo made six long visits to Rome, totaling over five hundred days, during which he met the pope, high-ranking members of the Church and the nobility, as well as leading figures of the literary and scientific establishment. His career can be seen in a novel and fascinating way when studied from the vantage point of the city where he was most anxious to be known and approved. This is what our work does for the first time. Each chapter corresponds to one trip, thereby providing a clear framework for the main events of Galileo’s life and allowing a fresh insight into the nature of the problems that he faced.
Galileo was deeply influenced by his close contacts with members of the ecclesiastical and the scientific community in Rome and, as time went on, he changed his agenda to fit new circumstances. He sometimes met with success, but he ultimately overplayed his hand and the outcome was dramatic. On the short term, his strategy was a failure; on the long term, he clearly emerged the winner.
The six trips occurred over a period of 46 years. The first took place in 1587, when Galileo, then 23 years old, went to Rome to meet scientists who might help him obtain a university appointment. With the assistance of Christopher Clavius, a Roman Jesuit professor, he got his first job at the University of Pisa in 1589 and, in 1592, he moved to the University of Padua, where he spent the next 18 years. After the publication of his astronomical discoveries had transformed him into a celebrity, Galileo returned to Florence, where he became the mathematician and philosopher of the grand duke of Tuscany. The next year, in 1611, he undertook a second and triumphal trip to Rome. He was made welcome by top-level members of the Church and the teaching profession. Unfortunately, his celebrity also gave rise to jealousy and opposition, especially when he began defending in public the Copernican view that the Earth is in motion and revolves around the Sun. This went against the commonsensical view that the Earth (and therefore humanity) is at the center of the universe, a belief that current scientific shared with tradition and Christian doctrine.
The opposition first arose among Aristotelian professors, but they soon managed to involve clerics who did not relish having to reinterpret Scripture in the light of new ideas. Galileo found out that he had been denounced to the Holy Office, and he traveled to Rome for the third time in December 1615 in order defend himself and avoid the condemnation of the heliocentric theory. He was brilliant in discussion, but to no avail. Copernicus’s book on the motion of the Earth was banned in 1616, and Galileo was admonished not to teach it. He returned to Florence and was silent on the matter until his friend and admirer Maffeo Barberini was elected pope in 1623, taking the name of Urban VIII. A year later Galileo made his fourth trip to Rome, where he was received six times by the pope. This trip was another triumph, and Galileo felt he could now publish his ideas as long as they were presented as conjectures. This is how his celebrated Dialogue on the Two Chief World Systems came to be written, and in 1630 Galileo made a fifth trip to Rome to request permission to print the book. A number of complications arose, and the work only appeared in Florence in 1632. A loud outcry was raised and Galileo was summoned to Rome, where he was put on trial in 1633. His book was censored, and he was condemned to prison, a sentence that was immediately commuted to house arrest.
The Galileo Affair remains as fascinating as ever, and it has much to teach us that is relevant to our own day. We believe it is the first step in a proper assessment of the relations between science and religion, and we hope that our account will help readers come to grips with the issue and enable them to answer for themselves questions that often arise concerning the affair. We have avoided technicalities, but the book is based on first-hand research and the reader will find the sources of our quotations at the end of the book. We have carefully checked out the slightest details and have been able to correct inaccuracies that are found in the best books on the subject. We have combined our respective knowledge of science and religion (one of us teaches history of science, and the other is a philosopher who is also a physicist and a Roman Catholic priest). The priest often saw Galileo’s point before the historian; the historian frequently reminded the priest that the Church had sound arguments.
CHAPTER ONE
Job Hunting and the Path to Rome
FIRST TRIP • 1587
In the autumn of 1587, a young man of 23 arrived from Florence on his first trip to the Eternal City. His name was Galileo Galilei, and, in accordance with an Italian custom of calling great men by their first name, we shall continue to refer to him as Galileo. In an age when class consciousness was on the rise in Italy, Galileo was proud of the fact that he descended from a noble family. Originally called Bonaiuti, they had exchanged that name for Galilei in the fourteenth century, although they
kept their coat of arms unchanged, a red stepladder on a gold shield, forming a pictograph of the word buonaiuti, which literally means good help. The first Galileo Galilei, the older brother of the young Galileo’s great-grandfather, was a successful doctor and an influential professor at the University of Florence. He also held high office in the Republic and was elected gonfaloniere or chief magistrate in 1445. He died around 1450 and was buried with public honors in the church of Santa Croce in Florence, where visitors to this day can admire his full-length marble figure in the floor of the nave, near the main entrance door. The second Galileo Galilei, the scientist who is the hero of our story, could not know in 1587 that he would one day become even more famous, and that his tomb would be erected in the same church, just a few meters away from the effigy of his ancestor.
Vincenzio, the father of our Galileo, lived in reduced circumstances but enjoyed a distinguished reputation as a lute player and a musical theorist. By his wife, Giulia Ammannati, Vincenzio had three sons, Galileo, Michelangelo, and Benedetto (who died in infancy), and four daughters of whom only two, Virginia and Livia, survived. The children were all given a musical training, and Galileo became a good organist as well as an outstanding lute player. He continued to play throughout his life, and he derived great solace from the instrument in later years, especially when blindness was added to his other afflictions. His younger brother, Michelangelo, became a music teacher and spent most of his professional career at the court of the Duke of Bavaria in Munich.
Galileo’s father supplemented his meager income as a musicologist by dealing in cloth and textile fabrics in the maritime city of Pisa, which was part of Tuscany. It is in this city that his eldest son, Galileo, was born on 15 February 1564, just three days before his celebrated countryman, the great artist and sculptor Michelangelo Buonarroti, closed his eyes in Rome.
Galileo received his early education in Pisa, but the family returned to Florence when he was ten years old. He was then sent to the Benedictine school of Vallombrosa, near Florence, but had to be removed because of an inflammation of his eyes, a problem that recurred later in life. He enrolled in the Faculty of Arts at the University of Pisa in September 1581 but left after three and a half years without taking a degree. This practice was not uncommon at the time, and it was not held against him when he later applied for a university post. Publications and good references were more useful than a piece of paper that said “Master” or “Doctor.”
The pages of the grand duke were given courses in mathematics by Ostilio Ricci and Galileo was allowed to attend them. He soon discovered that his real interest was not medicine, as he had thought, but mathematics, which was enjoying a great revival with the publication of the original writings of Euclid and Archimedes. This does not mean that Galileo neglected literature and the arts altogether, for around this time he drafted essays on some of the great Italian writers such as Dante, Ariosto, and Tasso. He also showed considerable skill in drawing and, had circumstances permitted him to choose his own career, he would have elected to become a painter. His talent as a draftsman and colorist later won him the admiration of some of the most famous artists of his day. Ludovico Cigoli, perhaps the best-known painter working in Rome at the beginning of the seventeenth century, used to say that Galileo had been his teacher in the art of perspective and that whatever reputation he enjoyed as an artist was due to his advice and encouragement.
EMPLOYMENT BECKONS
When he left the university in the summer of 1585, however, a career as a painter was out of the question. With his growing family and small means, Vincenzio expected his oldest son to get a job. Galileo agreed, and he began to give private lessons in mathematics to students in Florence and the neighboring city of Siena. However, he realized that this would not get him far. What he needed was a permanent job and, in mathematics, this meant a position in a university. Galileo decided to apply for the next vacancy that occurred, and in the meantime he knew what he had to do. First, he had to produce an original piece of work and, second, he needed good references. The first was a condition for the second, and while Galileo was casting about for a suitable topic he heard, perhaps from the lips of Ostilio Ricci, the famous story about Archimedes and the goldsmith who had been given a certain amount of gold to fashion a crown for Hiero, the ruler of Syracuse. When the work was finished, Hiero suspected that the goldsmith had swindled him by mixing the gold with some baser metal, and he applied to Archimedes in the hope of detecting the imposture.
The goldsmith had made sure that the crown weighed as much as the quantity of gold that had been supplied, but since silver, weight for weight, is of greater bulk than gold, if silver had been added, the crown would be bulkier. So much was certain, but the problem was to measure the bulk (and therefore test the purity of the metal) without destroying the work of art by melting the crown into a regular figure. Archimedes was almost driven to distraction by this conundrum, and he decided to take a break and go to the public baths. As he stepped into the pool, which was full to the rim, he realized that a quantity of water of the same bulk as his body must overflow before he could immerse himself completely. In a flash, he saw the solution to his problem and rushed out of the public bath, stark naked, calling out in Greek, “Eureka! Eureka!” (I have found it! I have found it!). Having calmed down somewhat, he returned to his house, procured two masses of metal, one of silver and the other of gold, each of equal weight as the crown. He filled a vessel with water right to the top and placed it in a larger container. He then plunged the mass of silver into the vessel and carefully collected the water that overflowed. He repeated the same procedure with the mass of gold and found that a smaller quantity of water had overflowed. Next he plunged the crown into the vessel and observed that it displaced more of the fluid than the gold had done but less than the silver. The crown was clearly neither pure gold nor pure silver but a mixture of both! This experiment made Galileo think as furiously as Archimedes himself. He realized that a more massive body such as gold is more closely compacted than a less massive one such as silver and, hence, weighs more per volume. He felt that Archimedes’s method, though correct in principle, was not rigorous enough, and he built an ingenious precision balance, what we now call a hydrostatical balance, to measure the respective weights of the metals more accurately.
The chair of mathematics at the University of Bologna was vacant and Galileo decided to try his chance. But practical skills, however important, were not enough to secure a position in a university. Original mathematical work was required, and Galileo decided to investigate geometrical problems related to the center of gravity of solids. The result was a paper that was not published in a journal because there was as yet no mathematical review, but it was put in circulation and sent to several eminent mathematicians including Giuseppe Moletti, the professor of mathematics at the University of Padua, and the Marquis Guidobaldo del Monte, the author of influential works on mathematics and mechanics. Both replied very graciously and congratulated the young man.
THE LEADING JESUIT MATHEMATICIAN
In Italy of the Counter Reformation, ecclesiastical support was not something to be neglected, and Galileo took steps to secure it by submitting his work to the Jesuits, who were considered the most learned and up-to-date order in the Catholic Church. Their main institution of higher learning was the Roman College, founded in 1551, and the professor of mathematics, Christopher Clavius, was celebrated all over Europe. A letter of recommendation by him would be worth its weight in gold.
The Society of Jesus was founded by Ignatius Loyola and approved by Pope Paul III in 1540. By 1581 there were over 5,000 members, and, in 1612, when a census was taken, they numbered 13,112 members. They excelled in teaching and by 1580 had opened 140 colleges, a number that rose to 245 at the beginning of the following century. They specialized in theology and philosophy, but they did not neglect mathematics and the natural sciences. Several Jesuits made important contributions to the advancement of learning, but the most successful was Ch
ristopher Clavius, who had left his native Bamberg in Germany to join the Society in Rome in 1555 when he was only 17. The years 1555 to 1557 were particularly difficult for the Jesuits because the election of Pope Paul IV created hostility between the papacy and Spain. The young Society, almost destitute, could not afford to maintain all their recruits in Rome, and for this reason many were dispersed to other Jesuit colleges. Thus Clavius was sent to study in Portugal in 1556 and returned to Rome four years later. He was ordained to the priesthood in 1564, the year of Galileo’s birth. Shortly thereafter he was appointed professor of mathematics at the Roman College, a post he was to occupy until his death in 1612.
CALENDAR REFORM
One of the highlights of Clavius’s career was the role he played in reforming the calendar as part of a commission that was instituted by Pope Gregory XIII in the mid-1570s. The Church saw this as a pressing matter because Easter, the main Christian feast, does not fall on a fixed date like Christmas but is celebrated by Western Christians on the first Sunday after the full moon that occurs upon or just after the vernal equinox. In practice this means between 22 March and 25 April. The Julian calendar, introduced under Julius Caesar in 46 B.C., was sorely out of step with the seasons and the equinoxes. This calendar, which assumed that the year contains exactly 365 days and a quarter, added an extra day every fourth year. Since the length of the year is actually a little less than 365 days and a quarter, this led to an error of about 3 days in every 400 years. The commission of Gregory XIII set matters right by omitting three leap years in every four centuries. Under the old scheme, any year was a leap year if its number was divisible by four. Under the new one, years whose numbers are divisible by 100 but not by 400 are not leap years. Hence 1800 and 1900 were not leap years, but 2000 was and 2400 will be. This reduces the error to about 1 day in 4,000 years. The Gregorian reform that was introduced in 1582 caught up with the real year by omitting ten days. Thus the day following 4 October 1582 was 15 October, 1582. Saint Theresa of Avila, the great Spanish mystic, died on the night of 4–15 October 1582. The reform may seem straightforward or even trivial to us but it gave rise to acrimonious debates. Workers feared that they would lose paydays, and riots erupted in many cities. Clavius had to spend a considerable amount of time explaining the bases and applications of the new calendar, with very limited success outside Catholic countries. The Gregorian calendar was not adopted in England until 1752 and in Russia only in 1918.
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