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Galileo Galilei -
Galileo, in full Galileo Galilei (born February 15, 1564, Pisa [Italy]—died January 8, 1642, Arcetri, near Florence), Italian natural philosopher, astronomer, and mathematician who made fundamental contributions to the sciences of motion, astronomy, and strength of materials and to the development of the scientific method. His formulation of (circular) inertia, the law of falling bodies, and parabolic trajectories marked the beginning of a fundamental change in the study of motion. His insistence that the book of nature was written in the language of mathematics changed natural philosophy from a verbal, qualitative account to a mathematical one in which experimentation became a recognized method for discovering the facts of nature. Finally, his discoveries with the telescope revolutionized astronomy and paved the way for the acceptance of the Copernican heliocentric system, but his advocacy of that system eventually resulted in an Inquisition process against him.
Early life and career
Galileo was born in Pisa, Tuscany, on February 15, 1564, the oldest son of Vincenzo Galilei, a musician who made important contributions to the theory and practice of music and who may have performed some experiments with Galileo in 1588–89 on the relationship between pitch and the tension of strings. The family moved to Florence in the early 1570s, where the Galilei family had lived for generations. In his middle teens Galileo attended the monastery school at Vallombrosa, near Florence, and then in 1581 matriculated at the University of Pisa, where he was to study medicine. However, he became enamoured with mathematics and decided to make the mathematical subjects and philosophy his profession, against the protests of his father. Galileo then began to prepare himself to teach Aristotelian philosophy and mathematics, and several of his lectures have survived. In 1585 Galileo left the university without having obtained a degree, and for several years he gave private lessons in the mathematical subjects in Florence and Siena. During this period he designed a new form of hydrostatic balance for weighing small quantities and wrote a short treatise, La bilancetta (“The Little Balance”), that circulated in manuscript form. He also began his studies on motion, which he pursued steadily for the next two decades.
In 1588 Galileo applied for the chair of mathematics at the University of Bologna but was unsuccessful. His reputation was, however, increasing, and later that year he was asked to deliver two lectures to the Florentine Academy, a prestigious literary group, on the arrangement of the world in Dante’s Inferno. He also found some ingenious theorems on centres of gravity (again, circulated in manuscript) that brought him recognition among mathematicians and the patronage of Guidobaldo del Monte (1545–1607), a nobleman and author of several important works on mechanics. As a result, he obtained the chair of mathematics at the University of Pisa in 1589. There, according to his first biographer, Vincenzo Viviani (1622–1703), Galileo demonstrated, by dropping bodies of different weights from the top of the famous Leaning Tower, that the speed of fall of a heavy object is not proportional to its weight, as Aristotle had claimed. The manuscript tract De motu (On Motion), finished during this period, shows that Galileo was abandoning Aristotelian notions about motion and was instead taking an Archimedean approach to the problem. But his attacks on Aristotle made him unpopular with his colleagues, and in 1592 his contract was not renewed. His patrons, however, secured him the chair of mathematics at the University of Padua, where he taught from 1592 until 1610.
Although Galileo’s salary was considerably higher there, his responsibilities as the head of the family (his father had died in 1591) meant that he was chronically pressed for money. His university salary could not cover all his expenses, and he therefore took in well-to-do boarding students whom he tutored privately in such subjects as fortification. He also sold a proportional compass, or sector, of his own devising, made by an artisan whom he employed in his house. Perhaps because of these financial problems, he did not marry, but he did have an arrangement with a Venetian woman, Marina Gamba, who bore him two daughters and a son. In the midst of his busy life he continued his research on motion, and by 1609 he had determined that the distance fallen by a body is proportional to the square of the elapsed time (the law of falling bodies) and that the trajectory of a projectile is a parabola, both conclusions that contradicted Aristotelian physics.
Telescopic discoveries
At this point, however, Galileo’s career took a dramatic turn. In the spring of 1609 he heard that in the Netherlands an instrument had been invented that showed distant things as though they were nearby. By trial and error, he quickly figured out the secret of the invention and made his own three-powered spyglass from lenses for sale in spectacle makers’ shops. Others had done the same; what set Galileo apart was that he quickly figured out how to improve the instrument, taught himself the art of lens grinding, and produced increasingly powerful telescopes. In August of that year he presented an eight-powered instrument to the Venetian Senate (Padua was in the Venetian Republic). He was rewarded with life tenure and a doubling of his salary. Galileo was now one of the highest-paid professors at the university. In the fall of 1609 Galileo began observing the heavens with instruments that magnified up to 20 times. In December he drew the Moon’s phases as seen through the telescope, showing that the Moon’s surface is not smooth, as had been thought, but is rough and uneven. In January 1610 he discovered four moons revolving around Jupiter. He also found that the telescope showed many more stars than are visible with the naked eye. These discoveries were earthshaking, and Galileo quickly produced a little book, Sidereus Nuncius (The Sidereal Messenger), in which he described them. He dedicated the book to Cosimo II de Medici (1590–1621), the grand duke of his native Tuscany, whom he had tutored in mathematics for several summers, and he named the moons of Jupiter after the Medici family: the Sidera Medicea, or “Medicean Stars.” Galileo was rewarded with an appointment as mathematician and philosopher of the grand duke of Tuscany, and in the fall of 1610 he returned in triumph to his native land.
Galileo was now a courtier and lived the life of a gentleman. Before he left Padua he had discovered the puzzling appearance of Saturn, later to be shown as caused by a ring surrounding it, and in Florence he discovered that Venus goes through phases just as the Moon does. Although these discoveries did not prove that the Earth is a planet orbiting the Sun, they undermined Aristotelian cosmology: the absolute difference between the corrupt earthly region and the perfect and unchanging heavens was proved wrong by the mountainous surface of the Moon, the moons of Jupiter showed that there had to be more than one centre of motion in the universe, and the phases of Venus showed that it (and, by implication, Mercury) revolves around the Sun. As a result, Galileo was confirmed in his belief, which he had probably held for decades but which had not been central to his studies, that the Sun is the centre of the universe and that the Earth is a planet, as Copernicus had argued. Galileo’s conversion to Copernicanism would be a key turning point in the scientific revolution.
After a brief controversy about floating bodies, Galileo again turned his attention to the heavens and entered a debate with Christoph Scheiner (1573–1650), a German Jesuit and professor of mathematics at Ingolstadt, about the nature of sunspots (of which Galileo was an independent discoverer). This controversy resulted in Galileo’s Istoria e dimostrazioni intorno alle macchie solari e loro accidenti (“History and Demonstrations Concerning Sunspots and Their Properties,” or “Letters on Sunspots”), which appeared in 1613. Against Scheiner, who, in an effort to save the perfection of the Sun, argued that sunspots are satellites of the Sun, Galileo argued that the spots are on or near the Sun’s surface, and he bolstered his argument with a series of detailed engravings of his observations.
Galileo’s Copernicanism
Galileo’s increasingly overt Copernicanism began to cause trouble for him. In 1613 he wrote a letter to his student Benedetto Castelli (1577–1644) in Pisa about the problem of squaring the Copernican theory with certain biblical passages. Inaccurate copies of this letter were sent by Galileo’s enemies to the Inquisition in Rome, and he had to retrieve the letter and send an accurate copy. Several Dominican fathers in Florence lodged complaints against Galileo in Rome, and Galileo went to Rome to defend the Copernican cause and his good name. Before leaving, he finished an expanded version of the letter to Castelli, now addressed to the grand duke’s mother and good friend of Galileo, the dowager Christina. In his Letter to the Grand Duchess Christina, Galileo discussed the problem of interpreting biblical passages with regard to scientific discoveries but, except for one example, did not actually interpret the Bible. That task had been reserved for approved theologians in the wake of the Council of Trent (1545–63) and the beginning of the Catholic Counter-Reformation. But the tide in Rome was turning against the Copernican theory, and in 1615, when the cleric Paolo Antonio Foscarini (c. 1565–1616) published a book arguing that the Copernican theory did not conflict with scripture, Inquisition consultants examined the question and pronounced the Copernican theory heretical. Foscarini’s book was banned, as were some more technical and nontheological works, such as Johannes Kepler’s Epitome of Copernican Astronomy. Copernicus’s own 1543 book, De revolutionibus orbium coelestium libri vi (“Six Books Concerning the Revolutions of the Heavenly Orbs”), was suspended until corrected. Galileo was not mentioned directly in the decree, but he was admonished by Robert Cardinal Bellarmine (1542–1621) not to “hold or defend” the Copernican theory. An improperly prepared document placed in the Inquisition files at this time states that Galileo was admonished “not to hold, teach, or defend” the Copernican theory “in any way whatever, either orally or in writing.”
Galileo was thus effectively muzzled on the Copernican issue. Only slowly did he recover from this setback. Through a student, he entered a controversy about the nature of comets occasioned by the appearance of three comets in 1618. After several exchanges, mainly with Orazio Grassi (1583–1654), a professor of mathematics at the Collegio Romano, he finally entered the argument under his own name. Il saggiatore (The Assayer), published in 1623, was a brilliant polemic on physical reality and an exposition of the new scientific method. Galileo here discussed the method of the newly emerging science, arguing:
Philosophy is written in this grand book, the universe, which stands continually open to our gaze. But the book cannot be understood unless one first learns to comprehend the language and read the letters in which it is composed. It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures without which it is humanly impossible to understand a single word of it.
He also drew a distinction between the properties of external objects and the sensations they cause in us—i.e., the distinction between primary and secondary qualities. Publication of Il saggiatore came at an auspicious moment, for Maffeo Cardinal Barberini (1568–1644), a friend, admirer, and patron of Galileo for a decade, was named Pope Urban VIII as the book was going to press. Galileo’s friends quickly arranged to have it dedicated to the new pope. In 1624 Galileo went to Rome and had six interviews with Urban VIII. Galileo told the pope about his theory of the tides (developed earlier), which he put forward as proof of the annual and diurnal motions of the Earth. The pope gave Galileo permission to write a book about theories of the universe but warned him to treat the Copernican theory only hypothetically. The book, Dialogo sopra i due massimi sistemi del mondo, tolemaico e copernicano (Dialogue Concerning the Two Chief World Systems, Ptolemaic & Copernican), was finished in 1630, and Galileo sent it to the Roman censor. Because of an outbreak of the plague, communications between Florence and Rome were interrupted, and Galileo asked for the censoring to be done instead in Florence. The Roman censor had a number of serious criticisms of the book and forwarded these to his colleagues in Florence. After writing a preface in which he professed that what followed was written hypothetically, Galileo had little trouble getting the book through the Florentine censors, and it appeared in Florence in 1632.
In the Dialogue’s witty conversation between Salviati (representing Galileo), Sagredo (the intelligent layman), and Simplicio (the dyed-in-the-wool Aristotelian), Galileo gathered together all the arguments (mostly based on his own telescopic discoveries) for the Copernican theory and against the traditional geocentric cosmology. As opposed to Aristotle’s, Galileo’s approach to cosmology is fundamentally spatial and geometric: the Earth’s axis retains its orientation in space as the Earth circles the Sun, and bodies not under a force retain their velocity (although this inertia is ultimately circular). But in giving Simplicio the final word, that God could have made the universe any way he wanted to and still made it appear to us the way it does, he put Pope Urban VIII’s favourite argument in the mouth of the person who had been ridiculed throughout the dialogue. The reaction against the book was swift. The pope convened a special commission to examine the book and make recommendations; the commission found that Galileo had not really treated the Copernican theory hypothetically and recommended that a case be brought against him by the Inquisition. Galileo was summoned to Rome in 1633. During his first appearance before the Inquisition, he was confronted with the 1616 edict recording that he was forbidden to discuss the Copernican theory. In his defense Galileo produced a letter from Cardinal Bellarmine, by then dead, stating that he was admonished only not to hold or defend the theory. The case was at somewhat of an impasse, and, in what can only be called a plea bargain, Galileo confessed to having overstated his case. He was pronounced to be vehemently suspect of heresy and was condemned to life imprisonment and was made to abjure formally. There is no evidence that at this time he whispered, “Eppur si muove” (“And yet it moves”). It should be noted that Galileo was never in a dungeon or tortured; during the Inquisition process he stayed mostly at the house of the Tuscan ambassador to the Vatican and for a short time in a comfortable apartment in the Inquisition building. (For a note on actions taken by Galileo’s defenders and by the church in the centuries since the trial, see BTW: Galileo’s condemnation.) After the process he spent six months at the palace of Ascanio Piccolomini (c. 1590–1671), the archbishop of Siena and a friend and patron, and then moved into a villa near Arcetri, in the hills above Florence. He spent the rest of his life there. Galileo’s daughter Sister Maria Celeste, who was in a nearby nunnery, was a great comfort to her father until her untimely death in 1634.
Galileo was then 70 years old. Yet he kept working. In Siena he had begun a new book on the sciences of motion and strength of materials. There he wrote up his unpublished studies that had been interrupted by his interest in the telescope in 1609 and pursued intermittently since. The book was spirited out of Italy and published in Leiden, Netherlands, in 1638 under the title Discorsi e dimostrazioni matematiche intorno a due nuove scienze attenenti alla meccanica (Dialogues Concerning Two New Sciences). Galileo here treated for the first time the bending and breaking of beams and summarized his mathematical and experimental investigations of motion, including the law of falling bodies and the parabolic path of projectiles as a result of the mixing of two motions, constant speed and uniform acceleration. By then Galileo had become blind, and he spent his time working with a young student, Vincenzo Viviani, who was with him when he died on January 8, 1642.
Excerpted from Encyclopedia Britannica
Other resources:
Link to watch PBS Documentary "Galileo's Battle for the Heavens"
Link to an interactive version of some of Galileo's experiments
Link to a short article describing "Galileo's Place in Science"
Link to a short blurb and video about how "Galileo's Telescope" was not invented by Galileo
Virginia Galilei -
Virginia, Galileo's oldest child, was born in Padua on 12 August 1600. Her mother, Marina Gamba, was Galileo's housekeeper. When Galileo moved to Florence, in 1610, he took Virginia and his other daughter, Livia (1601-1659), with him, leaving his son Vincenzio (only four years old) with his mother for a few years.
After he had settled in Florence, Galileo decided to put his two daughters in a convent for life. It took several years to make the arrangements. Not the least problem was that the girls were too young to make this important decision for themselves. Through the offices of Cardinal Maffeo Barberini, one of his admirers, Galileo obtained dispensation on this score, and in 1613 both girls were placed in the convent of San Matteo in nearby Arcetri, where the abbess was the sister of the secretary of the grand duke of Tuscany. Virginia took the veil in 1616, choosing the name of Sister Maria Celeste, and Livia followed the same course a year later, becoming Sister Arcangela.
Little is known about the life of Sister Maria Celeste until 1623, but about 120 letters to her father, written from 1623 to 1634 have survived. From these the picture of a loving daughter, always solicitous of her father's well being, emerges. Maria Celeste Celeste wrote to her father that the bread was bad, the wine sour and that they ate ox meat. Galileo helped repair windows and personally took charge of keeping the convent clock in good repair. Maria Celeste often had to appeal to her father for help, and she was chronically ill. She bore her ill health with dignity and courage, and managed to be a great comfort to her father. She worked constantly to mitigate the difficulties between Galileo and her brother Vincenzio.
In 1631 Galileo bought the villa "Il Goiello" in Arcetri, near the convent. From this house he could see San Matteo and hear its bells. It was here that he spent his final years under house arrest. Part of the sentence that Galileo received in 1633 read as follows: "As a salutary penance we impose on you to recite the seven penitential Psalms once a week for the next three years." Sister Maria Celeste took it upon herself to perform this penance for him. She died, however, on 2 April 1634, less than four months after Galileo's return to Arcetri.
Cosimo De Medici -
Cosimo II, in full Cosimo de’ Medici (born May 12, 1590—died Feb. 28, 1621), fourth grand duke of Tuscany (1609–20), who closed down the Medici family’s practice of banking and commerce, which it had pursued for four centuries. Cosimo II succeeded his father, Ferdinand I, in 1609; and, guided by his mother, Christine of Lorraine, and by Belisario Vinta, he followed his father’s example and sought to establish a balance between France and Spain. He used his influence to promote the Franco-Spanish negotiations of 1611–12, which led to the marriages of 1615 (between Louis XIII of France and Anne of Austria and between the future Philip IV of Spain and Elizabeth of France). His fleet, under the admirals Jacopo Inghirami and Giulio di Montauto, checked the Turks in the Mediterranean; and his friendly relations with the Druze emir Fakhr ad-Dīn secured commercial advantages in the Levant for Tuscans.
It was Cosimo who appointed Galileo “first professor of philosophy and mathematics” at Pisa and mathematician and philosopher of the grand duke of Tuscany in 1610, after Galileo discovered four satellites of Jupiter and named them the Sidera Medicea (“Medicean Stars”). Under Cosimo also the architect Matteo Nigetti worked on the funeral chapel of the Medici (according to designs by Cosimo I’s brilliant natural son, the younger Giovanni, who also won fame as a soldier and as a diplomat); and the sculptor Pietro Tacca began his bronzes for the monument to Ferdinand I. Cosimo abandoned all banking and commerce on his own account, for he considered it demeaning and distracting from the course of political governance.
Excerpted from Encyclopedia Britannica
Father Christopher Clavius -
Christopher Clavius (1537–1612) Jesuit astronomer
Nothing is known of Clavius's early life, except that he was born in Bamberg in the German region. In 1556 he was sent to the university of Coimbra in Portugal, where the Jesuits had founded their own college. Here he took the normal university curriculum but excelled in the mathematical subjects, and his observation of the total solar eclipse of 1560 made him decide that astronomy would be his life's work. In 1560 he returned to Rome and began his study of theology at the Collegio Romano. He was ordained in 1564 while still pursuing his theological studies. In 1575 he became a full member of the order. He began teaching the mathematical subjects at the college as early as 1564 and, except for a two-year stay in Naples, he was on the faculty of the Collegio Romano until his death in 1612.
As the foremost mathematician of the Jesuit order, Clavius wrote a number of textbooks, all of which went through numerous editions during his life. These include his version of Euclid's Elements, his commentary on the Sphere of Sacrobosco, and books on algebra, the astrolabe, and practical arithmetic and geometry. Clavius was the senior mathemtician on the commission for the reform of the calendar that led, in 1582, to the institution of the Gregorian calendar. Because of his prodigious output of mathematical works, he was called "the Euclid of the sixteenth century." Through his teaching and textbooks, and also through several mathematical curricula drafted by him, Clavius shaped mathematical education in the Jesuit order all over the world.
In his astronomical books, Clavius opposed the Copernican System on both physical and scriptural grounds. Until near the end of his life he remained an adherent of the Ptolemaic System. From his university days, Galileo was familiar with Clavius's books, and he visited the famous man during his first trip to Rome in 1587. After that they corresponded from time to time about mathematical problems, and Clavius sent Galileo copies of his books as they appeared. The publication of Sidereus Nuncius, in 1610, posed a serious problem for Clavius and his mathematical colleagues in the Collegio Romano. Their opinion of the new phenomena discovered by Galileo was sought by Catholics everywhere, but Clavius and his colleagues did not have instruments good enough to verify them. Clavius was initially skeptical, but by the end of 1610 he and other mathematicians of the college had confirmed the existence of the satellites of Jupiter and seen the phases of Venus. In April 1611, during Galileo's visit to Rome, they certified the phenomena revealed by the telescope as real. Clavius was, however, very cautious in his interpretation of several of them, especially the meaning of the rough appearance of the Moon. The phases of Venus made the Ptolemaic arrangement of the planets untenable. As Clavius cautiously noted here, an alternative arrangement had to be found. One could modify Ptolemy's scheme and have Mercury and Venus go around the Sun while the Sun and all other bodies go around the Earth. This scheme had already been proposed in Antiquity, but it had never been in the mainstream of astronomy and cosmology because it posited two centers of rotation in the universe. The satellites of Jupiter had now shown that no matter what arrangement one preferred, there was more than one center of rotation.
Excerpted from Galileo Project
Cardinal Barberini (subsequently Pope Urban VIII) -
Urban VIII, original name Maffeo Barberini (baptized April 5, 1568, Florence—died July 29, 1644, Rome), pope from 1623 to 1644. The son of an aristocratic Florentine family, Barberini filled many distinguished church appointments. He served as papal legate in France (1601) and was simultaneously appointed (1604) archbishop of Nazareth and nuncio to Paris. Pope Paul V made him cardinal in 1606 and bishop of Spoleto in 1608. He became an astute politician during these years, acquiring many friends and making few enemies. He was elected Pope Gregory XV’s successor on Aug. 6, 1623.
Urban’s pontificate coincided with the ministry of Cardinal de Richelieu of France and with the decisive period of the Thirty Years’ War. His policy, when contrasted with that of his successor, Innocent X, appears to have been decidedly pro-French and hostile to the Roman Catholic cause in Germany. In fact, he desired the extinction of Protestantism everywhere, but, because he ultimately feared Habsburg domination in Italy, he withheld his support from them and allied with their enemy Richelieu. This alliance destroyed the Habsburgs’ claim to be considered the exclusive champions of Roman Catholicism and so turned the Thirty Years’ War into a conflict of dynastic interests that resulted not so much in the triumph of Protestantism as in the ruin of Germany.
Determined to strengthen the papacy’s material resources and defense, Urban greatly fortified the Castel Sant’Angelo in Rome (1624–41). He also erected Fort Urbano at Castelfranco, transformed Civitavecchia into a flourishing port with a military harbour, and enlarged the arsenal at Tivoli. The Duchy of Urbino was acquired by the pope in 1626, and the Papal States became a compact, well-defended bloc dominating central Italy. Unfortunately, concurrent with his expensive fortifications and defense plan, Urban was guilty of unrestrained opulence and large-scale nepotism. His building program—which included the grandiose papal villa at Castel Gandolfo and extravagant piazzas and fountains—combined with the enrichment of his family, tended to squander the financial resources of the papacy.
In an endeavour to establish supremacy over northern Italy, Urban began the War of Castro (1642–44) against Duke Odoardo I Farnese of Parma, whom he excommunicated in 1642, but the campaign ended in the pope’s defeat and humiliation in March 1644. Venice, Tuscany, and Modena then formed an antipapal league to protect Parma, and France also intervened in Odoardo’s favour. Peace was concluded at Venice on March 31, 1644, and Urban died soon afterward.
A promoter of the arts, Urban VIII was the foremost patron of the important Baroque sculptor and architect Gian Lorenzo Bernini, some of whose finest works he commissioned, including the loggias of St. Peter’s, Rome, and Urban’s tomb in the basilica. Reluctantly, he had his friend Galileo tried and condemned for a short time in 1633.
Excerpted from Encyclopedia Britannica
Cardinal Bellarmin -
Saint Robert Bellarmine, Italian in full San Roberto Francesco Romolo Bellarmino (born Oct. 4, 1542, Montepulciano, Tuscany [Italy]—died Sept. 17, 1621, Rome; canonized 1930; feast day Sept. 17), Italian cardinal and theologian, an opponent of the Protestant doctrines of the Reformation.
Bellarmine entered the Society of Jesus in 1560. After studying in Italy at Rome, Mondovì, and Padua, he was sent to Leuven (Louvain) in the Spanish Netherlands, where he was ordained in 1570 and began to teach theology. He was forced by the strength of Protestantism and the Augustinian doctrines of grace and free will prevailing in the Low Countries to define his theological principles. He returned to Rome, where he lectured at the new Jesuit College. Made a cardinal by Pope Clement VIII in 1599, he was subsequently appointed archbishop of Capua (1602). As a consultor of the Holy Office, he took a prominent part in the first examination of Galileo’s writings. Bellarmine, somewhat sympathetic to Galileo’s views, granted him an audience in which he warned him not to defend the Copernican theory but to regard it only as a hypothesis. Acting on the part of the Holy Office, and fearing scandal at a time when Roman Catholicism and Protestantism were embroiled, Bellarmine thought it best to have the Copernican theory declared “false and erroneous.” The church so decreed in 1616.
Excerpted from Encyclopedia Britannica
Galileo Galilei -
Galileo, in full Galileo Galilei (born February 15, 1564, Pisa [Italy]—died January 8, 1642, Arcetri, near Florence), Italian natural philosopher, astronomer, and mathematician who made fundamental contributions to the sciences of motion, astronomy, and strength of materials and to the development of the scientific method. His formulation of (circular) inertia, the law of falling bodies, and parabolic trajectories marked the beginning of a fundamental change in the study of motion. His insistence that the book of nature was written in the language of mathematics changed natural philosophy from a verbal, qualitative account to a mathematical one in which experimentation became a recognized method for discovering the facts of nature. Finally, his discoveries with the telescope revolutionized astronomy and paved the way for the acceptance of the Copernican heliocentric system, but his advocacy of that system eventually resulted in an Inquisition process against him.
Early life and career
Galileo was born in Pisa, Tuscany, on February 15, 1564, the oldest son of Vincenzo Galilei, a musician who made important contributions to the theory and practice of music and who may have performed some experiments with Galileo in 1588–89 on the relationship between pitch and the tension of strings. The family moved to Florence in the early 1570s, where the Galilei family had lived for generations. In his middle teens Galileo attended the monastery school at Vallombrosa, near Florence, and then in 1581 matriculated at the University of Pisa, where he was to study medicine. However, he became enamoured with mathematics and decided to make the mathematical subjects and philosophy his profession, against the protests of his father. Galileo then began to prepare himself to teach Aristotelian philosophy and mathematics, and several of his lectures have survived. In 1585 Galileo left the university without having obtained a degree, and for several years he gave private lessons in the mathematical subjects in Florence and Siena. During this period he designed a new form of hydrostatic balance for weighing small quantities and wrote a short treatise, La bilancetta (“The Little Balance”), that circulated in manuscript form. He also began his studies on motion, which he pursued steadily for the next two decades.
In 1588 Galileo applied for the chair of mathematics at the University of Bologna but was unsuccessful. His reputation was, however, increasing, and later that year he was asked to deliver two lectures to the Florentine Academy, a prestigious literary group, on the arrangement of the world in Dante’s Inferno. He also found some ingenious theorems on centres of gravity (again, circulated in manuscript) that brought him recognition among mathematicians and the patronage of Guidobaldo del Monte (1545–1607), a nobleman and author of several important works on mechanics. As a result, he obtained the chair of mathematics at the University of Pisa in 1589. There, according to his first biographer, Vincenzo Viviani (1622–1703), Galileo demonstrated, by dropping bodies of different weights from the top of the famous Leaning Tower, that the speed of fall of a heavy object is not proportional to its weight, as Aristotle had claimed. The manuscript tract De motu (On Motion), finished during this period, shows that Galileo was abandoning Aristotelian notions about motion and was instead taking an Archimedean approach to the problem. But his attacks on Aristotle made him unpopular with his colleagues, and in 1592 his contract was not renewed. His patrons, however, secured him the chair of mathematics at the University of Padua, where he taught from 1592 until 1610.
Although Galileo’s salary was considerably higher there, his responsibilities as the head of the family (his father had died in 1591) meant that he was chronically pressed for money. His university salary could not cover all his expenses, and he therefore took in well-to-do boarding students whom he tutored privately in such subjects as fortification. He also sold a proportional compass, or sector, of his own devising, made by an artisan whom he employed in his house. Perhaps because of these financial problems, he did not marry, but he did have an arrangement with a Venetian woman, Marina Gamba, who bore him two daughters and a son. In the midst of his busy life he continued his research on motion, and by 1609 he had determined that the distance fallen by a body is proportional to the square of the elapsed time (the law of falling bodies) and that the trajectory of a projectile is a parabola, both conclusions that contradicted Aristotelian physics.
Telescopic discoveries
At this point, however, Galileo’s career took a dramatic turn. In the spring of 1609 he heard that in the Netherlands an instrument had been invented that showed distant things as though they were nearby. By trial and error, he quickly figured out the secret of the invention and made his own three-powered spyglass from lenses for sale in spectacle makers’ shops. Others had done the same; what set Galileo apart was that he quickly figured out how to improve the instrument, taught himself the art of lens grinding, and produced increasingly powerful telescopes. In August of that year he presented an eight-powered instrument to the Venetian Senate (Padua was in the Venetian Republic). He was rewarded with life tenure and a doubling of his salary. Galileo was now one of the highest-paid professors at the university. In the fall of 1609 Galileo began observing the heavens with instruments that magnified up to 20 times. In December he drew the Moon’s phases as seen through the telescope, showing that the Moon’s surface is not smooth, as had been thought, but is rough and uneven. In January 1610 he discovered four moons revolving around Jupiter. He also found that the telescope showed many more stars than are visible with the naked eye. These discoveries were earthshaking, and Galileo quickly produced a little book, Sidereus Nuncius (The Sidereal Messenger), in which he described them. He dedicated the book to Cosimo II de Medici (1590–1621), the grand duke of his native Tuscany, whom he had tutored in mathematics for several summers, and he named the moons of Jupiter after the Medici family: the Sidera Medicea, or “Medicean Stars.” Galileo was rewarded with an appointment as mathematician and philosopher of the grand duke of Tuscany, and in the fall of 1610 he returned in triumph to his native land.
Galileo was now a courtier and lived the life of a gentleman. Before he left Padua he had discovered the puzzling appearance of Saturn, later to be shown as caused by a ring surrounding it, and in Florence he discovered that Venus goes through phases just as the Moon does. Although these discoveries did not prove that the Earth is a planet orbiting the Sun, they undermined Aristotelian cosmology: the absolute difference between the corrupt earthly region and the perfect and unchanging heavens was proved wrong by the mountainous surface of the Moon, the moons of Jupiter showed that there had to be more than one centre of motion in the universe, and the phases of Venus showed that it (and, by implication, Mercury) revolves around the Sun. As a result, Galileo was confirmed in his belief, which he had probably held for decades but which had not been central to his studies, that the Sun is the centre of the universe and that the Earth is a planet, as Copernicus had argued. Galileo’s conversion to Copernicanism would be a key turning point in the scientific revolution.
After a brief controversy about floating bodies, Galileo again turned his attention to the heavens and entered a debate with Christoph Scheiner (1573–1650), a German Jesuit and professor of mathematics at Ingolstadt, about the nature of sunspots (of which Galileo was an independent discoverer). This controversy resulted in Galileo’s Istoria e dimostrazioni intorno alle macchie solari e loro accidenti (“History and Demonstrations Concerning Sunspots and Their Properties,” or “Letters on Sunspots”), which appeared in 1613. Against Scheiner, who, in an effort to save the perfection of the Sun, argued that sunspots are satellites of the Sun, Galileo argued that the spots are on or near the Sun’s surface, and he bolstered his argument with a series of detailed engravings of his observations.
Galileo’s Copernicanism
Galileo’s increasingly overt Copernicanism began to cause trouble for him. In 1613 he wrote a letter to his student Benedetto Castelli (1577–1644) in Pisa about the problem of squaring the Copernican theory with certain biblical passages. Inaccurate copies of this letter were sent by Galileo’s enemies to the Inquisition in Rome, and he had to retrieve the letter and send an accurate copy. Several Dominican fathers in Florence lodged complaints against Galileo in Rome, and Galileo went to Rome to defend the Copernican cause and his good name. Before leaving, he finished an expanded version of the letter to Castelli, now addressed to the grand duke’s mother and good friend of Galileo, the dowager Christina. In his Letter to the Grand Duchess Christina, Galileo discussed the problem of interpreting biblical passages with regard to scientific discoveries but, except for one example, did not actually interpret the Bible. That task had been reserved for approved theologians in the wake of the Council of Trent (1545–63) and the beginning of the Catholic Counter-Reformation. But the tide in Rome was turning against the Copernican theory, and in 1615, when the cleric Paolo Antonio Foscarini (c. 1565–1616) published a book arguing that the Copernican theory did not conflict with scripture, Inquisition consultants examined the question and pronounced the Copernican theory heretical. Foscarini’s book was banned, as were some more technical and nontheological works, such as Johannes Kepler’s Epitome of Copernican Astronomy. Copernicus’s own 1543 book, De revolutionibus orbium coelestium libri vi (“Six Books Concerning the Revolutions of the Heavenly Orbs”), was suspended until corrected. Galileo was not mentioned directly in the decree, but he was admonished by Robert Cardinal Bellarmine (1542–1621) not to “hold or defend” the Copernican theory. An improperly prepared document placed in the Inquisition files at this time states that Galileo was admonished “not to hold, teach, or defend” the Copernican theory “in any way whatever, either orally or in writing.”
Galileo was thus effectively muzzled on the Copernican issue. Only slowly did he recover from this setback. Through a student, he entered a controversy about the nature of comets occasioned by the appearance of three comets in 1618. After several exchanges, mainly with Orazio Grassi (1583–1654), a professor of mathematics at the Collegio Romano, he finally entered the argument under his own name. Il saggiatore (The Assayer), published in 1623, was a brilliant polemic on physical reality and an exposition of the new scientific method. Galileo here discussed the method of the newly emerging science, arguing:
Philosophy is written in this grand book, the universe, which stands continually open to our gaze. But the book cannot be understood unless one first learns to comprehend the language and read the letters in which it is composed. It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures without which it is humanly impossible to understand a single word of it.
He also drew a distinction between the properties of external objects and the sensations they cause in us—i.e., the distinction between primary and secondary qualities. Publication of Il saggiatore came at an auspicious moment, for Maffeo Cardinal Barberini (1568–1644), a friend, admirer, and patron of Galileo for a decade, was named Pope Urban VIII as the book was going to press. Galileo’s friends quickly arranged to have it dedicated to the new pope. In 1624 Galileo went to Rome and had six interviews with Urban VIII. Galileo told the pope about his theory of the tides (developed earlier), which he put forward as proof of the annual and diurnal motions of the Earth. The pope gave Galileo permission to write a book about theories of the universe but warned him to treat the Copernican theory only hypothetically. The book, Dialogo sopra i due massimi sistemi del mondo, tolemaico e copernicano (Dialogue Concerning the Two Chief World Systems, Ptolemaic & Copernican), was finished in 1630, and Galileo sent it to the Roman censor. Because of an outbreak of the plague, communications between Florence and Rome were interrupted, and Galileo asked for the censoring to be done instead in Florence. The Roman censor had a number of serious criticisms of the book and forwarded these to his colleagues in Florence. After writing a preface in which he professed that what followed was written hypothetically, Galileo had little trouble getting the book through the Florentine censors, and it appeared in Florence in 1632.
In the Dialogue’s witty conversation between Salviati (representing Galileo), Sagredo (the intelligent layman), and Simplicio (the dyed-in-the-wool Aristotelian), Galileo gathered together all the arguments (mostly based on his own telescopic discoveries) for the Copernican theory and against the traditional geocentric cosmology. As opposed to Aristotle’s, Galileo’s approach to cosmology is fundamentally spatial and geometric: the Earth’s axis retains its orientation in space as the Earth circles the Sun, and bodies not under a force retain their velocity (although this inertia is ultimately circular). But in giving Simplicio the final word, that God could have made the universe any way he wanted to and still made it appear to us the way it does, he put Pope Urban VIII’s favourite argument in the mouth of the person who had been ridiculed throughout the dialogue. The reaction against the book was swift. The pope convened a special commission to examine the book and make recommendations; the commission found that Galileo had not really treated the Copernican theory hypothetically and recommended that a case be brought against him by the Inquisition. Galileo was summoned to Rome in 1633. During his first appearance before the Inquisition, he was confronted with the 1616 edict recording that he was forbidden to discuss the Copernican theory. In his defense Galileo produced a letter from Cardinal Bellarmine, by then dead, stating that he was admonished only not to hold or defend the theory. The case was at somewhat of an impasse, and, in what can only be called a plea bargain, Galileo confessed to having overstated his case. He was pronounced to be vehemently suspect of heresy and was condemned to life imprisonment and was made to abjure formally. There is no evidence that at this time he whispered, “Eppur si muove” (“And yet it moves”). It should be noted that Galileo was never in a dungeon or tortured; during the Inquisition process he stayed mostly at the house of the Tuscan ambassador to the Vatican and for a short time in a comfortable apartment in the Inquisition building. (For a note on actions taken by Galileo’s defenders and by the church in the centuries since the trial, see BTW: Galileo’s condemnation.) After the process he spent six months at the palace of Ascanio Piccolomini (c. 1590–1671), the archbishop of Siena and a friend and patron, and then moved into a villa near Arcetri, in the hills above Florence. He spent the rest of his life there. Galileo’s daughter Sister Maria Celeste, who was in a nearby nunnery, was a great comfort to her father until her untimely death in 1634.
Galileo was then 70 years old. Yet he kept working. In Siena he had begun a new book on the sciences of motion and strength of materials. There he wrote up his unpublished studies that had been interrupted by his interest in the telescope in 1609 and pursued intermittently since. The book was spirited out of Italy and published in Leiden, Netherlands, in 1638 under the title Discorsi e dimostrazioni matematiche intorno a due nuove scienze attenenti alla meccanica (Dialogues Concerning Two New Sciences). Galileo here treated for the first time the bending and breaking of beams and summarized his mathematical and experimental investigations of motion, including the law of falling bodies and the parabolic path of projectiles as a result of the mixing of two motions, constant speed and uniform acceleration. By then Galileo had become blind, and he spent his time working with a young student, Vincenzo Viviani, who was with him when he died on January 8, 1642.
Excerpted from Encyclopedia Britannica
Other resources:
Link to watch PBS Documentary "Galileo's Battle for the Heavens"
Link to an interactive version of some of Galileo's experiments
Link to a short article describing "Galileo's Place in Science"
Link to a short blurb and video about how "Galileo's Telescope" was not invented by Galileo
Virginia Galilei -
Virginia, Galileo's oldest child, was born in Padua on 12 August 1600. Her mother, Marina Gamba, was Galileo's housekeeper. When Galileo moved to Florence, in 1610, he took Virginia and his other daughter, Livia (1601-1659), with him, leaving his son Vincenzio (only four years old) with his mother for a few years.
After he had settled in Florence, Galileo decided to put his two daughters in a convent for life. It took several years to make the arrangements. Not the least problem was that the girls were too young to make this important decision for themselves. Through the offices of Cardinal Maffeo Barberini, one of his admirers, Galileo obtained dispensation on this score, and in 1613 both girls were placed in the convent of San Matteo in nearby Arcetri, where the abbess was the sister of the secretary of the grand duke of Tuscany. Virginia took the veil in 1616, choosing the name of Sister Maria Celeste, and Livia followed the same course a year later, becoming Sister Arcangela.
Little is known about the life of Sister Maria Celeste until 1623, but about 120 letters to her father, written from 1623 to 1634 have survived. From these the picture of a loving daughter, always solicitous of her father's well being, emerges. Maria Celeste Celeste wrote to her father that the bread was bad, the wine sour and that they ate ox meat. Galileo helped repair windows and personally took charge of keeping the convent clock in good repair. Maria Celeste often had to appeal to her father for help, and she was chronically ill. She bore her ill health with dignity and courage, and managed to be a great comfort to her father. She worked constantly to mitigate the difficulties between Galileo and her brother Vincenzio.
In 1631 Galileo bought the villa "Il Goiello" in Arcetri, near the convent. From this house he could see San Matteo and hear its bells. It was here that he spent his final years under house arrest. Part of the sentence that Galileo received in 1633 read as follows: "As a salutary penance we impose on you to recite the seven penitential Psalms once a week for the next three years." Sister Maria Celeste took it upon herself to perform this penance for him. She died, however, on 2 April 1634, less than four months after Galileo's return to Arcetri.
Cosimo De Medici -
Cosimo II, in full Cosimo de’ Medici (born May 12, 1590—died Feb. 28, 1621), fourth grand duke of Tuscany (1609–20), who closed down the Medici family’s practice of banking and commerce, which it had pursued for four centuries. Cosimo II succeeded his father, Ferdinand I, in 1609; and, guided by his mother, Christine of Lorraine, and by Belisario Vinta, he followed his father’s example and sought to establish a balance between France and Spain. He used his influence to promote the Franco-Spanish negotiations of 1611–12, which led to the marriages of 1615 (between Louis XIII of France and Anne of Austria and between the future Philip IV of Spain and Elizabeth of France). His fleet, under the admirals Jacopo Inghirami and Giulio di Montauto, checked the Turks in the Mediterranean; and his friendly relations with the Druze emir Fakhr ad-Dīn secured commercial advantages in the Levant for Tuscans.
It was Cosimo who appointed Galileo “first professor of philosophy and mathematics” at Pisa and mathematician and philosopher of the grand duke of Tuscany in 1610, after Galileo discovered four satellites of Jupiter and named them the Sidera Medicea (“Medicean Stars”). Under Cosimo also the architect Matteo Nigetti worked on the funeral chapel of the Medici (according to designs by Cosimo I’s brilliant natural son, the younger Giovanni, who also won fame as a soldier and as a diplomat); and the sculptor Pietro Tacca began his bronzes for the monument to Ferdinand I. Cosimo abandoned all banking and commerce on his own account, for he considered it demeaning and distracting from the course of political governance.
Excerpted from Encyclopedia Britannica
Father Christopher Clavius -
Christopher Clavius (1537–1612) Jesuit astronomer
Nothing is known of Clavius's early life, except that he was born in Bamberg in the German region. In 1556 he was sent to the university of Coimbra in Portugal, where the Jesuits had founded their own college. Here he took the normal university curriculum but excelled in the mathematical subjects, and his observation of the total solar eclipse of 1560 made him decide that astronomy would be his life's work. In 1560 he returned to Rome and began his study of theology at the Collegio Romano. He was ordained in 1564 while still pursuing his theological studies. In 1575 he became a full member of the order. He began teaching the mathematical subjects at the college as early as 1564 and, except for a two-year stay in Naples, he was on the faculty of the Collegio Romano until his death in 1612.
As the foremost mathematician of the Jesuit order, Clavius wrote a number of textbooks, all of which went through numerous editions during his life. These include his version of Euclid's Elements, his commentary on the Sphere of Sacrobosco, and books on algebra, the astrolabe, and practical arithmetic and geometry. Clavius was the senior mathemtician on the commission for the reform of the calendar that led, in 1582, to the institution of the Gregorian calendar. Because of his prodigious output of mathematical works, he was called "the Euclid of the sixteenth century." Through his teaching and textbooks, and also through several mathematical curricula drafted by him, Clavius shaped mathematical education in the Jesuit order all over the world.
In his astronomical books, Clavius opposed the Copernican System on both physical and scriptural grounds. Until near the end of his life he remained an adherent of the Ptolemaic System. From his university days, Galileo was familiar with Clavius's books, and he visited the famous man during his first trip to Rome in 1587. After that they corresponded from time to time about mathematical problems, and Clavius sent Galileo copies of his books as they appeared. The publication of Sidereus Nuncius, in 1610, posed a serious problem for Clavius and his mathematical colleagues in the Collegio Romano. Their opinion of the new phenomena discovered by Galileo was sought by Catholics everywhere, but Clavius and his colleagues did not have instruments good enough to verify them. Clavius was initially skeptical, but by the end of 1610 he and other mathematicians of the college had confirmed the existence of the satellites of Jupiter and seen the phases of Venus. In April 1611, during Galileo's visit to Rome, they certified the phenomena revealed by the telescope as real. Clavius was, however, very cautious in his interpretation of several of them, especially the meaning of the rough appearance of the Moon. The phases of Venus made the Ptolemaic arrangement of the planets untenable. As Clavius cautiously noted here, an alternative arrangement had to be found. One could modify Ptolemy's scheme and have Mercury and Venus go around the Sun while the Sun and all other bodies go around the Earth. This scheme had already been proposed in Antiquity, but it had never been in the mainstream of astronomy and cosmology because it posited two centers of rotation in the universe. The satellites of Jupiter had now shown that no matter what arrangement one preferred, there was more than one center of rotation.
Excerpted from Galileo Project
Cardinal Barberini (subsequently Pope Urban VIII) -
Urban VIII, original name Maffeo Barberini (baptized April 5, 1568, Florence—died July 29, 1644, Rome), pope from 1623 to 1644. The son of an aristocratic Florentine family, Barberini filled many distinguished church appointments. He served as papal legate in France (1601) and was simultaneously appointed (1604) archbishop of Nazareth and nuncio to Paris. Pope Paul V made him cardinal in 1606 and bishop of Spoleto in 1608. He became an astute politician during these years, acquiring many friends and making few enemies. He was elected Pope Gregory XV’s successor on Aug. 6, 1623.
Urban’s pontificate coincided with the ministry of Cardinal de Richelieu of France and with the decisive period of the Thirty Years’ War. His policy, when contrasted with that of his successor, Innocent X, appears to have been decidedly pro-French and hostile to the Roman Catholic cause in Germany. In fact, he desired the extinction of Protestantism everywhere, but, because he ultimately feared Habsburg domination in Italy, he withheld his support from them and allied with their enemy Richelieu. This alliance destroyed the Habsburgs’ claim to be considered the exclusive champions of Roman Catholicism and so turned the Thirty Years’ War into a conflict of dynastic interests that resulted not so much in the triumph of Protestantism as in the ruin of Germany.
Determined to strengthen the papacy’s material resources and defense, Urban greatly fortified the Castel Sant’Angelo in Rome (1624–41). He also erected Fort Urbano at Castelfranco, transformed Civitavecchia into a flourishing port with a military harbour, and enlarged the arsenal at Tivoli. The Duchy of Urbino was acquired by the pope in 1626, and the Papal States became a compact, well-defended bloc dominating central Italy. Unfortunately, concurrent with his expensive fortifications and defense plan, Urban was guilty of unrestrained opulence and large-scale nepotism. His building program—which included the grandiose papal villa at Castel Gandolfo and extravagant piazzas and fountains—combined with the enrichment of his family, tended to squander the financial resources of the papacy.
In an endeavour to establish supremacy over northern Italy, Urban began the War of Castro (1642–44) against Duke Odoardo I Farnese of Parma, whom he excommunicated in 1642, but the campaign ended in the pope’s defeat and humiliation in March 1644. Venice, Tuscany, and Modena then formed an antipapal league to protect Parma, and France also intervened in Odoardo’s favour. Peace was concluded at Venice on March 31, 1644, and Urban died soon afterward.
A promoter of the arts, Urban VIII was the foremost patron of the important Baroque sculptor and architect Gian Lorenzo Bernini, some of whose finest works he commissioned, including the loggias of St. Peter’s, Rome, and Urban’s tomb in the basilica. Reluctantly, he had his friend Galileo tried and condemned for a short time in 1633.
Excerpted from Encyclopedia Britannica
Cardinal Bellarmin -
Saint Robert Bellarmine, Italian in full San Roberto Francesco Romolo Bellarmino (born Oct. 4, 1542, Montepulciano, Tuscany [Italy]—died Sept. 17, 1621, Rome; canonized 1930; feast day Sept. 17), Italian cardinal and theologian, an opponent of the Protestant doctrines of the Reformation.
Bellarmine entered the Society of Jesus in 1560. After studying in Italy at Rome, Mondovì, and Padua, he was sent to Leuven (Louvain) in the Spanish Netherlands, where he was ordained in 1570 and began to teach theology. He was forced by the strength of Protestantism and the Augustinian doctrines of grace and free will prevailing in the Low Countries to define his theological principles. He returned to Rome, where he lectured at the new Jesuit College. Made a cardinal by Pope Clement VIII in 1599, he was subsequently appointed archbishop of Capua (1602). As a consultor of the Holy Office, he took a prominent part in the first examination of Galileo’s writings. Bellarmine, somewhat sympathetic to Galileo’s views, granted him an audience in which he warned him not to defend the Copernican theory but to regard it only as a hypothesis. Acting on the part of the Holy Office, and fearing scandal at a time when Roman Catholicism and Protestantism were embroiled, Bellarmine thought it best to have the Copernican theory declared “false and erroneous.” The church so decreed in 1616.
Excerpted from Encyclopedia Britannica