IX. GALILEO: 1564–1642

1. The Physicist

Galileo Galilei was born at Pisa on the day of Michelangelo’s death (February 18, 1564), in the same year as Shakespeare. His father was a cultured Florentine, who shared in teaching him Greek, Latin, mathematics, and music. Not for nothing was Galileo an almost exact contemporary of Monteverdi (1567–1643); music was one of his perennial consolations, especially in his blind old age; he played the organ creditably and the lute well. He liked to draw and paint, and sometimes he regretted that he had not become an artist. In that wonderful Italy of his youth the flame of the Renaissance still burned, inspiring men to be complete. He mourned that he could not design a temple, carve a statue, paint a portrait, write poetry, compose music, guide a ship;77 he longed to do all of these; and we feel, as we contemplate him, that he lacked only time. Such a man, under different accidents, could have been any kind of great man. Whether by nature or by circumstance, he turned in boyhood to making and playing with machines.

At seventeen he was sent to the University of Pisa to study medicine and philosophy. A year later he made his first scientific discovery—that the swings of a pendulum, regardless of their width, take equal times. By lengthening or shortening the arm of a pendulum he could retard or quicken the rate of oscillation until it synchronized with his pulse; by this “pulsilogia” he could accurately measure his heartbeat.

About this time he discovered Euclid. He overheard a tutor teaching geometry to the pages of the Grand Duke of Tuscany; the logic of mathematics seemed to him immeasurably superior to the Scholastic and Aristotelian philosophy that he had received in the classroom; clandestinely, with Euclid’s Elements in his hand, he followed the lessons of the instructor to the pages. The tutor took an interest in him and taught him privately. In 1585 Galileo left the University of Pisa without taking a degree, moved to Florence, and, under the tutor’s guidance, gave himself with passion to mathematics and mechanics. A year later he invented a hydrostatic balance to measure the relative weights of metals in an alloy, and won the praise of the Jesuit Clavius for an essay on the center of gravity in solid bodies. Meanwhile his father’s means ran out, and Galileo faced the obligation to earn his own bread. He applied for teaching posts at Pisa, Florence, and Padua; he was rejected as too young. In 1589, as he and a friend were planning to seek their fortunes in Constantinople and the East, they heard that the chair of mathematics at Pisa had fallen vacant. Galileo applied for it in forlorn hope; he was still only twenty-five. He was given a three-year appointment, at sixty scudi per year. On this he could starve, but he could show his mettle.

He was mettlesome enough, for he began at once, from his professorial chair, a war on the physics of Aristotle. According to the Greek “the downward movement of a mass of gold or lead, or of any other body endowed with weight, is quicker in proportion to its size.”78 Lucretius79 and Leonardo da Vinci80 expressed the same view. Even in antiquity Hipparchus (c. 130 B.C.) had questioned the opinion of Aristotle “on bodies carried downward through weight”; and Joannes Philoponus (533 A.D.), commenting on Aristotle, thought that the difference in time of fall between two objects one of which is twice the weight of the other will be “either none at all or imperceptible.”81 Here we come upon a famous and disputed story. It appears first in an early biography of Galileo, written by his friend Vincenzo Viviani in 1654 (twelve years after Galileo’s death), and claiming to be founded on Galileo’s own verbal account:

To the dismay of all the philosophers, very many conclusions of Aristotle were by him [Galileo] proved false through experiments and solid demonstrations … as, among others, that the velocity of moving bodies of the same material, of unequal weight, moving through the same medium, did not mutually preserve the proportion of their weight as taught by Aristotle, but all moved at the same speed; demonstrating this with repeated experiments from the height of the Campanile of Pisa in the presence of the other teachers and philosophers, and the whole assembly of students…. He upheld the dignity of this professional chair with so great fame … that many philosophasters, his rivals, stirred with envy, were aroused against him.82

Galileo himself nowhere mentions the Pisa experiment in his extant writings; neither is it mentioned by two of his contemporaries who in 1612 and 1641 reported their own experiments in dropping objects of diverse weight from the top of the Leaning Tower.83Viviani’s story has been rejected as a legend by some scholars in Germany and America.Iv Uncertain, too, is the tradition concerning the resentment of fellow professors at Pisa. He left that university in the summer of 1592, probably because he had been offered a loftier chair at a better fee. In September we find him installed at the University of Padua, teaching geometry, mechanics, and astronomy, and turning his home into a laboratory to which he invited his students and friends. He avoided marriage, but took a mistress, who gave him three children.

Now he made the researches and experiments that he gathered together only toward the end of his life in his Dialogues Concerning Two New Sciences—i.e., concerning statics and dynamics. He affirmed the indestructibility of matter. He formulated the principles of the lever and the pulley, and showed that the speed of freely falling bodies increases at a uniform rate. He made many experiments with inclined planes; he argued that an object rolling down one plane would rise on a similar plane to a height equal to its fall if it were not for frictional or other resistance; and he concluded to the law of inertia (Newton’s first law of motion)—that a moving body will continue indefinitely in the same line and rate of motion unless interfered with by some external force.84 He proved that a projectile propelled in a horizontal direction would fall to the earth in a parabolic curve compounding the forces of impetus and gravity. He reduced musical tones to wave lengths of air, and showed that the pitch of a note depends upon the number of vibrations made by the struck string in a given time. Notes, he taught, are felt as consonant and harmonious when their vibrations strike the ear with rhythmic regularity.85 Only those properties of matter belong to matter that can be dealt with mathematically—extension, position, motion, density; all other properties—sounds, tastes, odors, colors, and so on—”reside only in consciousness; if the living creature were removed, all these qualities would be wiped away and annihilated.”86 He hoped that in time these “secondary qualities” could be analyzed into primary physical qualities of matter and motion, mathematically measurable.87

These were basic and fruitful contributions. They were hampered by inadequacy of instruments; so, for example, Galileo underestimated the factor of air resistance in the fall of objects and projectiles. But no man since Archimedes had ever done so much for physics.

2. The Astronomer

Toward the end of his stay in Padua he gave more and more of his time to astronomy. In a letter (1596) to Kepler (seven years his junior), thanking him for the Mysterium cosmographicum, he wrote:

I esteem myself happy to have as great an ally as you in my search for truth. … I will read your work … all the more willingly because I have for many years been a partisan of the Copernican view, and because it reveals to me the causes of many natural phenomena that are entirely incomprehensible in the light of the generally accepted hypotheses. To refute the latter I have collected many proofs, but I do not publish them, because I am deterred by the fate of our teacher Copernicus, who, though he had won immortal fame with a few, was ridiculed and condemned by countless people (for very great is the number of the stupid). I would dare to publish my speculations if there were more people like you.88

He professed his Copernican faith in a lecture at Pisa in 1604. In 1609 he made his first telescope, and on August 21 he demonstrated it to Venetian officials. Hear his account:

Many of the nobles and senators, although of a great age, mounted more than once to the top of the highest church in Venice [St. Mark’s], in order to see sails and shipping … so far off that it was two hours before they were seen without my spyglass …, for the effect of my instrument is such that it makes an object fifty miles off appear as large as if it were only five miles away…. The Senate, knowing the way in which I had served it for seventeen years at Padua, … ordered my election to the professorship for life.89

He improved his telescope until it magnified objects a thousand times. Turning it to the sky, he was amazed to discover a new world of stars, ten times as many as had yet been catalogued. Constellations were now seen to contain a great number of stars invisible to the unaided eye; so the Pleiades were seen to be thirty-six instead of seven and Orion eighty instead of thirty-seven, and the Milky Way appeared not as a nebulous mass but as a forest of stars great or small. The moon was no longer a smooth surface, but a corrugation of mountains and valleys; and the vague illumination of its unsunned half could be explained as partly due to sunshine reflected from the earth. In January 1610 Galileo discovered four of the nine “moons” or satellites of Jupiter; “these new bodies,” he wrote, “moved around another very great star, in the same way as Mercury and Venus, and peradventure the other known planets, move around the sun.”90 In July he discovered the ring of Saturn, which he mistook for three stars. Critics of Copernicus had argued that if Venus revolved around the sun it should, like the moon, show phases—changes in illumination and apparent shape; and they had held that there was no sign of such changes. But in December Galileo’s telescope revealed such phases, and he believed that they could be explained only by the planet’s revolution around the sun.

It seems unbelievable, but Galileo, in a letter to Kepler, affirmed that the professors at Padua refused to credit his discoveries, refused even to look at the skies through his telescopes.91 Tiring of Padua, and hoping for a better intellectual climate in Florence (which was passing from art to science), Galileo named the satellites of Jupiter the Sidera Medicea after Cosimo II, Grand Duke of Tuscany. In March 1610 he dedicated to Cosimo a Latin treatise, Sidereus nuncius, summarizing his astronomical revelations. In May he wrote to the Duke’s secretary a letter warm with the ardor and pride of Leonardo’s appeal to the Duke of Milan in 1482. He listed the subjects that he was studying and the books in which he hoped to describe his results, and he wondered if he might secure from his master an appointment that would require less time for teaching and leave more for research. In June Cosimo named him “First Mathematician of the University of Pisa, and First Mathematician and Philosopher to the Grand Duke,” with an annual salary of a thousand florins, and without obligation to teach. In September Galileo moved to Florence, without his concubine.

He had insisted on the title of philosopher as well as mathematician, for he wished to influence philosophy as well as science. He felt as Ramus, Bruno, Telesio, and others had done before him, as Bacon was urging in this same decade, that philosophy (which he understood as the study and interpretation of Nature in all its aspects) had gone to sleep in the lap of Aristotle, and that the time had come to escape from these forty Greek volumes and look at the world with loosened categories and open eyes and mind. Possibly he trusted too much to reason. “To demonstrate to my opponents the truth of my conclusions, I have been forced to prove them by a variety of experiments, though to satisfy myself alone I have never felt it necessary to make many.”92

He had the pride and pugnacity of an innovator, though at times he spoke with a wise modesty—”I have never met a man so ignorant that I could not learn something from him.”93 He was an ardent controversialist, skilled to spear a foe on a phrase or roast him with burning indignation. In the margin of a book by the Jesuit Antonio Rocco defending the Ptolemaic astronomy, Galileo wrote, “Ignoramus, elephant, fool, dunce … eunuch.”94

But that was after the Jesuits had joined in condemning him. Before his encounter with the Inquisition he had many friends in the Society of Jesus. Christopher Clavius confirmed Galileo’s observations with his own; another Jesuit lauded Galileo as the greatest astronomer of the age; a commission of Jesuit scholars, appointed by Cardinal Bellarmine to examine Galileo’s findings, reported favorably on all points.95 When he went to Rome in 1611 the Jesuits entertained him at their Collegium Romanum. “I stayed with the Jesuit fathers,” he wrote; “they had verified the actual existence of the new planets and had been constantly observing them for two months; we compared notes, and I found that their observations agreed exactly with my own.”96 He was welcomed by dignitaries of the Church, and Pope Paul V assured him of his unalterable good will.97

In April he showed to prelates and scientists in Rome the results of observations that revealed spots on the sun, which he interpreted as clouds. Apparently unknown to Galileo, Johannes Fabricius had already announced their discovery in De maculis solis(Wittenberg, 1611) and had anticipated Galileo’s conclusion that the periodicity of the spots indicated the rotation of the sun. In 1615 Christoph Scheiner, Jesuit professor of mathematics at Ingolstadt, addressed to Markus Welser, chief magistrate of Augsburg, three letters in which he claimed to have discovered the spots in April 1611. Galileo, back in Florence, received from Welser a copy of Scheiner’s communications. He discussed them in Three Letters on the Solar Spots, published at Rome by the Accademia dei Lincei in 1613. He claimed that he had observed the spots in 1610 and had shown them to friends in Padua. In the clash of claims to priority in discovering the spots, the friendship between Galileo and the Jesuits cooled.

Convinced that his findings could be explained only on the Copernican theory, Galileo began to talk of the theory as proved. The Jesuit astronomers had no objection to considering it as a hypothesis. Scheiner sent his objections to the Copernican view to Galileo, with a conciliatory letter. “If you wish to advance counterarguments,” he wrote, “we shall in no way be offended by them, but will, on the contrary, gladly examine your arguments in the hope that all this will assist in the elucidation of the truth.”98 Many theologians felt that the Copernican astronomy was so clearly incompatible with the Bible that if it prevailed the Bible would lose authority and Christianity itself would suffer. What would happen to the fundamental Christian belief that God had chosen this earth as His human home—this earth now to be shorn of its primacy and dignity, to be set loose among planets so many times larger than itself, and among innumerable stars?

3. On Trial

Galileo met the problem uncompromisingly. “Inasmuch as the Bible,” he wrote to Father Castelli (December 21, 1613), “calls for an interpretation differing from the immediate sense of the words” (as when it speaks of God’s anger, hatred, remorse, hands, and feet), “it seems to me that as an authority in mathematical controversy it has very little standing. … I believe that natural processes which we either perceive by careful observation or deduce by cogent demonstration cannot be refuted by passages from the Bible.”99Cardinal Bellarmine was alarmed. Through common friends he sent to Galileo a pointed admonition. “It seems to me,” he wrote to the astronomer’s pupil Foscarini, “that you and Galileo would be well advised to speak not in absolute terms [of the new astronomy as proved] but ex suppositione, as I am convinced that Copernicus himself did.”100

On December 21, 1614, a Dominican preacher, Tommaso Caccini, began the attack, taking as his text an excellent pun, Viri Galilei, quid statis aspicientes in coelum?—”Ye men of Galilee, why stand ye gazing up into the heavens?” (Acts, i, II)—and proceeding to show that the Copernican theory was in irresoluble conflict with the Bible. Other minor warriors sent complaints to the Inquisition; and on March 20, 1615, Cassini lodged a formal accusation against Galileo before the Congregation of the Holy office (the inquisition). Monsignor Dini wrote to Galileo that if he would insert into his publications a few sentences declaring the Copernican view to be hypothesis, he would not be disturbed,101 but Galileo refused, as he put it, to “moderate” Copernicus. In a letter to the Grand Duchess of Tuscany, published in 1615, he wrote with bold clarity: “As to the arrangement of the parts of the universe, I hold the sun to be situated motionless in the center of the revolution of the celestial orbs,V while the earth rotates on its axis and revolves about the sun.”102 He went on to a broader heresy:

Nature … is inexorable and immutable; she never transgresses the laws imposed upon her, or cares a whit whether her abstruse reasons and methods of operation are understandable to men. For that reason it appears that nothing physical which sense-experience sets before our eyes, or which necessary demonstrations prove to us, ought to be called in question (much less condemned) upon the testimony of Biblical passages which may have some different meaning beneath their words.

However, he promised submission to the Church:

I declare (and my sincerity will make itself manifest) not only that I mean to submit myself freely and renounce any errors into which I may fall in this discourse through ignorance of matters pertaining to religion, but that I do not desire in these matters to engage in disputes with anyone…. My goal is this alone: that if, among errors that may abound in these considerations of a subject remote from my profession, there is anything that may be serviceable to the holy Church in making a decision concerning the Copernican system, it may be taken and utilized as seems best to the superiors. And if not, let my book be torn and burned, as I neither intend nor pretend to gain from it any fruit that is not pious and Catholic.103

But he added, “I do not feel obliged to believe that that same God who has endowed us with sense, reason, and intellect has intended us to forgo their use.”104

On December 3, 1615, he went to Rome of his own accord, armed with friendly letters from the Grand Duke to influential prelates and the Florentine ambassador at the Vatican. In Rome he undertook to convert ecclesiastical officials individually; he upheld the Copernican system at every opportunity; soon “everybody” in Rome was discussing the stars.105 On February 26, 1616, the Inquisition directed Cardinal Bellarmine to “summon before him the said Galileo and admonish him to abandon the said opinions, and in case of refusal … to intimate to him, before a notary and witnesses, a command to abstain altogether from teaching or defending the said opinions and even from discussing them. If he do not acquiesce therein he is to be imprisoned.”106 Galileo appeared before Cardinal Bellarmine on that day and declared his submission to the decree.107 On March 5 the Holy Office published its historic edict:

The view that the sun stands motionless at the center of the universe is foolish, philosophically false, and utterly heretical, because contrary to Holy Scripture. The view that the earth is not the center of the universe and even has a daily rotation is philosophically false, and at least an erroneous belief.108

The Congregation of the Index, on the same date, forbade the publication or reading of any book advocating the condemned doctrines; but in the case of Copernicus’ De revolutionibus orbium coelestium (1543) it forbade the use of the book “until it is corrected”; and in 1620 it allowed Catholics to read editions from which nine sentences that represented the theory as a fact had been removed.

Galileo returned to Florence, lived in studious retirement in his villa, Bellosguardo, and kept out of controversy till 1622. In 1619 his disciple Mario Guiducci published an essay embodying Galileo’s theory (now rejected) that comets are emanations of the earth’s atmosphere, and vigorously criticizing the views of the Jesuit Orazio Grassi. The irate father, under a pseudonym, published an attack upon Galileo and his followers. In 1622 Galileo sent to Monsignor Cesarini in Rome the manuscript of Il saggiatore (The Assayer), answering Grassi, and rejecting, in science, all authority but observation, reason, and experiment. With the author’s consent some members of the Accademia dei Lincei softened a few passages. In this form Urban VIII accepted its dedication and sanctioned its publication (October 1623). It is Galileo’s most brilliant composition, a masterpiece of Italian prose and controversial skill. The Pope, we are told, enjoyed it; the Jesuits squirmed.

So encouraged, Galileo set out again for Rome (April 1, 1624), hoping to convert the new Pope to Copernican ideas. Urban received him cordially, gave him six long interviews and many gifts, listened to the Copernican arguments, but refused to lift the Inquisition’s ban. Galileo went back to Florence consoled by Urban’s declaration to the Grand Duke, “For a long time we have extended our fatherly love to this great man, whose fame shines in heaven and marches on earth.”109 In 1626 Galileo was heartened by the appointment of his pupil Benedetto Castelli to be mathematician to the Pope, and of another pupil, Father Niccolo Riccardi, as chief censor of the press. He hastened now to complete his chief work, an exposition of the Copernican and anti-Copernican systems. In May he took the manuscript to Rome, showed it to the Pope, and obtained the ecclesiastical imprimatur for its publication, on condition that the subject be treated as hypothesis. Back in Florence, Galileo revised the book and issued it (February 1632) under a long title: Dialogo … dei due massimi sistemi del mundo—Dialogue of G. G., … Where, in Meetings of Four Days, Are Discussed the Two Chief Systems of the World, Ptolemaic and Copernican, Indeterminately Proposing the Philosophical and Natural Arguments, as Well on One Side as on the Other.

The book might have brought Galileo less grief and renown had it not been for its beginning and its end. Said the preface “to the discerning reader”:

Several years ago there was published in Rome a salutary edict which, in order to obviate the dangerous tendencies of our present age, imposed a reasonable silence upon the Pythagorean opinion that the earth moves. There were those who impudently asserted that this decree had its origin not in judicious inquiry, but in passion none too well informed. Complaints were to be heard that advisers who were totally unskilled in astronomical observations ought not to clip the wings of reflective intellects by means of rash prohibitions.110

This was in effect to notify the reader that the dialogue form was a dodge to elude the Inquisition. In the dialogue two characters, Salviati and Sagredo—the names of two of Galileo’s warmest friends—defend the Copernican system; a third character, Simplicio, rejects it, but with transparent sophistry. Near the end of the work Galileo put into Simplicio’s mouth, almost verbatim, a statement that Urban VIII had insisted on being added: “God is all-powerful; all things are therefore possible to him; ergo the tides cannot be adduced as a necessary proof of the double motion of the earth without limiting God’s omniscience.” Upon which Salviati comments sarcastically, “An admirable and truly angelic argument.”111

The Jesuits, several of whom were roughly handled in the Dialogue (Scheiner’s ideas were called “vain and foolish”), pointed out to the Pope that his statement had been put into the mouth of a character who throughout the book had been represented as a simpleton. Urban appointed a commission to examine the work; it reported that Galileo had treated the Copernican system not as hypothesis but as fact, and that he had secured the imprimatur by clever misrepresentations. The Jesuits added, with foresight, that the doctrines of Copernicus and Galileo were more dangerous to the Church than all the heresies of Luther and Calvin. In August 1632 the Inquisition forbade further sale of the Dialogue, and ordered the confiscation of all remaining copies. On September 23 it summoned Galileo to appear before its commissioner in Rome. His friends pleaded his sixty-eight years and many infirmities, but to no avail. His daughter, now a fervent nun, sent him touching letters begging him to submit to the Church. The Grand Duke advised him to obey, provided him with the grand-ducal sedan chair, and arranged with the Florentine ambassador to house him in the embassy. Galileo reached Rome February 13, 1633.

Two months passed before the Inquisition called him to its palace (April 12). He was charged with having broken his promise to obey the decree of February 26, 1616, and was urged to confess his guilt. He refused, protesting that he had only presented the Copernican view as hypothesis. He was kept a prisoner in the palace of the Inquisition till April 30. There he fell sick. He was not put to torture, but may have been led to fear it. At a second appearance before the commission he humbly confessed that he had stated the case for Copernicus more strongly than against him, and offered to correct this in a supplementary dialogue. He was allowed to return to the house of the ambassador. On May 10 he was examined again; he offered to do penance and begged consideration for his age and ill health. At a fourth examination (June 21) he affirmed that after the decree of 1616 “every doubt vanished from my mind, and I held and still hold Ptolemy’s opinion—that the earth is motionless and that the sun moves—as absolutely true and incontestable.”112 The Inquisition countered that Galileo’s dialogues made quite clear his acceptance of Copernicus; Galileo insisted that he had been anti-Copernican since 1616. The Pope had kept in touch with the examination, but had not attended in person. Galileo hoped that Urban VIII would come to his aid, but the Pope refused to interfere. On June 22 the Inquisition pronounced him guilty of heresy and disobedience; it offered him absolution on condition of full abjuration; it sentenced him to “the prison of this Holy Office for a period determinable at our pleasure,” and prescribed as penance the recitation of the seven penitential psalms daily for the next three years. He was made to kneel, repudiate the Copernican theory, and add:

With a sincere heart and unfeigned faith I abjure, curse, and detest the said errors and heresies, and generally every other error and heresy contrary to the … Holy Church, and I swear that I will nevermore in future say or assert anything … which may give rise to a similar suspicion of me; and that if I shall know any heretic or anyone suspected of heresy, I will denounce him to this Holy Office. … So may God help me, and these His Holy Gospels which I touch with my own hands.113

The sentence was signed by seven cardinals, but did not receive papal ratification.114 The story that on leaving the trial chamber Galileo muttered defiantly, “Eppur si muove!” (And yet it does move!), is a legend not traceable before 1761.115 After three days in the prison of the Inquisition he was allowed, by order of the Pope, to go to the villa of the Grand Duke at Trinità dei Monti in Rome; a week later he was transferred to comfortable quarters in the palace of his former pupil, Archbishop Ascanio Piccolomini, at Siena. In December 1633 he was allowed to remove to his own villa at Arcetri, near Florence. Technically he was still a prisoner, and he was forbidden to wander outside his own grounds, but he was free to pursue his studies, teach pupils, write books, and receive visitors—here Milton came in 1638. His nun daughter came to live with him, and took upon herself the penalty of reciting the psalms.

4. The Patriarch

Apparently he was a broken man, defeated and humiliated by a Church that felt herself the guardian of the faith, hopes, and morals of mankind. His abjuration, after months of imprisonment and days of questioning that could have shattered the mind and will of a young warrior, was forgivable in an old man who remembered Bruno’s burning thirty-three years before. But he was not really defeated. His book spread through Europe in a dozen translations, and his book did not recant.

He solaced his grief at Siena and Arcetri by summing up his physical researches in another major work, Discorsiedimostraúoni matematiche intorno a due nuove scienze (Dialogues … Concerning Two New Sciences). As the Italian press was closed to him by his condemnation, he negotiated secretly with foreign printers, and finally the Elzevir firm issued the book at Leiden in 1638. It was acclaimed throughout the learned world as raising the science of mechanics to a higher level than ever before. After its publication he continued to prepare additional dialogues, in which he studied the mechanics of percussion and adumbrated Newton’s second law of motion. “In the last days of his life,” says his first biographer, “and amid much physical suffering, his mind was constantly occupied with mechanical and mathematical problems.”116 In 1637, just before his eyesight began to fail, he announced his last astronomical discovery, the librations of the moon—the variations in that side of the moon which always faces the earth. And in 1641, a few months before his death, he explained to his son a plan for making a pendulum clock.

The portrait that Sustermans painted of him at Arcetri (now in the Pitti Gallery) is of genius incarnate: immense forehead, pugnacious lips, searching nose, penetrating eyes; this is one of the noblest faces in history. The eyes lost their sight in 1638, perhaps from too arduous gazing. He consoled himself with the thought that no man since Adam had seen so much as he. “This universe,” he said, “that I have extended a thousand times … has now shrunk to the narrow confines of my own body. Thus God likes it; so I too must like it.”117 In 1639, suffering from sleeplessness and a hundred pains, he was allowed by the Inquisition to visit Florence, under strict surveillance, to see a physician and hear Mass. Back in Arcetri he dictated to Viviani and Torricelli and played the lute, till his hearing also failed. On January 8, 1642, aged almost seventy-eight, he died in the arms of his disciples.

Grotius called him “the greatest mind of all time.”118 He had, of course, some limitations of intellect and character. His faults—pride, temper, vanity—were literally the defects or price of his qualities: his persistence, courage, and originality. He did not recognize the importance of Kepler’s calculations on the planetary orbits. He was slow to credit the work of his contemporaries. He hardly realized how many of his discoveries in mechanics had been made before him—some by another Florentine, Leonardo. The views for which he was punished are not precisely those that astronomers hold today; like most martyrs, he suffered for the right to be wrong. But he was not wrong in feeling that he had made dynamics a full-fledged science and had widened the human mind and perspective by revealing, in greater measure than ever before, the frightful immensity of the universe. He shared with Kepler the honor of winning acceptance for Copernicus, and with Newton the distinction of showing that the heavens declare the glory of law. And, like a good son of the Renaissance, he wrote the best Italian prose of his time.

His influence pervaded Europe. His very condemnation raised the status of science in northern lands, while lowering it for a while in Italy and Spain. Not that the Inquisition destroyed Italian science: Torricelli, Cassini, Borelli, Redi, Malpighi, Morgagni carried the torch on to Volta, Galvani, and Marconi. But Italian scientists, remembering Galileo, avoided the philosophical implications of science. After the burning of Bruno and the intimidation of Descartes by Galileo’s fate, European philosophy became a Protestant monopoly.

In 1835 the Church withdrew the works of Galileo from her Index of Prohibited Books. The broken and defeated man had triumphed over the most powerful institution in history.

I. For superstition, science, and philosophy in England in this period cf. Chapter VII.

II.Jena (1558), Geneva (1559), Lille (1562), Strasbourg (1567), Leiden (1575), Helmstedt (1575), Wilno (1578), Würzburg (1582), Edinburgh (1583), Franeker (1585), Graz (1596), Dublin (1591), Lublin (1596), Harderwijk (1600), Giessen (1607), Groningen (1614), Amsterdam (1632), Dorpat (1632), Budapest (1635), Utrecht (1636), Turku (1640), Bamberg (1648).

III. Ideally the calendar would have thirteen months, each of twenty-eight days, with a dateless holiday (or, in leap years, two) at the close of the year. Such a one-page calendar, with rotary devices to indicate the month and the year, could serve for every month indefinitely; each day of the week would fall on the same dates every month and every year; the business year would be evenly divisible into equal months and equal quarters. But, alas, this would confuse the saints.

IV. Aristotle’s writings are often syncopated notes, which he probably amplified or modified in lecturing. The passage in De Coelo may have meant that in a resisting medium, including open air, objects of concentrated mass, like a coin, fall faster than articles great in size but small in weight, like a sheet of paper; this, of course, is true. But in a vacuum the coin and the paper—or a ball of lead and a feather—fall at the same speed; and even in the open air the paper, if crumpled into a compact mass, falls at nearly the same speed as the coin. If we note the modification in Viviani’s statement—that the objects must be “of the same material … falling through the same medium”—the divergence between the Athenian philosopher and the Pisan scientist is much reduced.

V. By the humor of history this is a proposition that no astronomer holds today. Perhaps all astronomy, like all history, should be taken as hypothesis. Of the beyond, as of yesterday, there is no certainty.

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