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Galileo: Watcher of the Skies

Copyright Date: 2010
Published by: Yale University Press
Pages: 354
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  • Book Info
    Book Description:

    Galileo (1564-1642) is one of the most important and controversial figures in the history of science. A hero of modern science and key to its birth, he was also a deeply divided man: a scholar committed to the establishment of scientific truth yet forced to concede the importance of faith, and a brilliant analyst of the elegantly mathematical workings of nature yet bungling and insensitive with his own family.

    Tackling Galileo as astronomer, engineer, and author, David Wootton places him at the center of Renaissance culture. He traces Galileo through his early rebellious years; the beginnings of his scientific career constructing a "new physics"; his move to Florence seeking money, status, and greater freedom to attack intellectual orthodoxies; his trial for heresy and narrow escape from torture; and his house arrest and physical (though not intellectual) decline. Wootton reveals much that is new-from Galileo's premature Copernicanism to a previously unrecognized illegitimate daughter-and, controversially, rejects the long-established orthodoxy which holds that Galileo was a good Catholic.

    Absolutely central to Galileo's significance-and to science more broadly-is the telescope, the potential of which Galileo was the first to grasp. Wootton makes clear that it totally revolutionized and galvanized scientific endeavor to discover new and previously unimagined facts. Drawing extensively on Galileo's voluminous letters, many of which were self-censored and sly, this is an original, arresting, and highly readable biography of a difficult, remarkable Renaissance genius.

    eISBN: 978-0-300-17006-1
    Subjects: History, History of Science & Technology

Table of Contents

  1. Front Matter
    (pp. i-vi)
  2. Table of Contents
    (pp. vii-viii)
  3. List of Illustrations
    (pp. ix-x)
  4. [Illustrations]
    (pp. None)
  5. Acknowledgements
    (pp. xi-xii)
  6. Introduction: Conjectural history
    (pp. 1-6)

    Our knowledge of Galileo’s life we owe largely to three people. One of these is Vincenzo Viviani (1622–1703), his last student, who was sixteen when he met Galileo and not yet twenty when his master died.² Viviani wrote Galileo’s first biography (which was not published until 1717), preserved his papers, and planned an edition of his complete works. When Viviani died, his property passed first to his nephew and then, in 1737, to the nephews of his nephew. These last did not share their great-uncle’s preoccupation with Galileo – despite the fact that 1737 was the year in which Galileo...

  7. Part one: The mind’s eye

    • 1 His father’s son
      (pp. 9-13)

      Galileo’s father Vincenzo (c.1525–91) was a Florentine musician. In 1562 he appears in Pisa, where he marries and sets up a music school. We do not know whether he first moved there for love or for money, though we may suspect that neither the marriage nor the music school flourished. The marriage took place on 5 July 1562, and Galileo, the eldest child, was born on 15 February 1564.² Surviving documents include accounts supplied by a good friend of Galileo’s father, Muzio Tedaldi, who handled his affairs during 1573 (when Galileo was aged nine – Muzio’s expenses include the purchase...

    • 2 Florence
      (pp. 14-17)

      Galileo was born in Pisa, spent much of his childhood there, went to university there, and got his first proper job there. But Viviani thought it important to stress that his father was a Florentine gentleman (albeit one who had fallen on hard times) who just happened to spend a few years in Pisa and marry there. Throughout his life Galileo referred to himself as a Florentine gentleman, ‘nobil fiorentino’.¹ Italians frequently identify people by the towns they come from – Leonardo da Vinci, Pietro Perugino – and the Pisans (and some others too) naturally call Galileo ‘il pisano’. This would not...

    • 3 Galileo’s lamp
      (pp. 18-21)

      Now for Galileo’s intellectual life. It is worth acknowledging what lies ahead of us. There is far too little information about Galileo’s intellectual life in the period from 1581, when he became a university student, to 1610, when he became famous. Much of my argument over the following pages will of necessity be tentative and conjectural. If an account existed on which we could rely I would not hesitate to provide a bald summary and move on, but none of the existing accounts will do.

      What the next few chapters attempt to trace is a double process. First there is...

    • 4 Eureka!
      (pp. 22-24)

      After three-and-a-half years studying medicine in Pisa, Galileo returned to Florence in 1585 to study mathematics openly. He was now working only for his own satisfaction. He quickly progressed from Euclid to Archimedes, whose key works had been available in print only since 1544. Archimedes was a revelation. Throughout the rest of his life, Galileo’s admiration for Archimedes, the Greek mathematician, engineer and scientist of the third century BC, knew no bounds. ‘It is all too obvious that no one else has ever been nearly as clever as he was.’¹ He is the ‘superhuman Archimedes, whose name I never mention...

    • 5 Seeing is believing
      (pp. 25-29)

      Shortly after writingThe Little Balance, in the last months of 1587, Galileo sent to the leading mathematicians of northern Italy his solutions to a problem that derived from Archimedes’ work.¹ He had been working on this problem for a couple of years. It had apparently been presented to him by the Marchese Guidobaldo del Monte, who was to become Galileo’s first patron, and whose work was to have a significant influence on Galileo up to the time of Guidobaldo’s death in 1607.² The issue was how to calculate the centre of gravity of various solids, and Galileo remained sufficiently...

    • 6 A friend in need
      (pp. 30-32)

      We know all too little about the early part of Galileo’s life, before he became famous with the publication ofThe Starry Messenger. Even after 1610, what we see of Galileo is mainly what he wanted us to see: those thoughts and feelings he chose to conceal have long seemed forever lost. There is, however, one source which enables us to, as it were, spy on Galileo and watch how he responds to an extremely difficult and morally demanding situation.¹

      In early 1589 Galileo was trying to establish himself as a mathematician, and doing some tutoring on the side – it...

    • 7 Juvenilia
      (pp. 33-35)

      This detour through a Florentine court case brings us to the most vexed issue in modern Galileo scholarship. It is an issue to which William Wallace OP devoted seven entire books, while unfortunately his most vigorous opponents, Alistair Crombie and Adriano Carugo, disagreed with everything but the central, mistaken premise of his argument.¹ So let us first make that central premise clear. At the very end of his life, in 1640, Galileo described himself to an opponent, Fortunio Liceti, as a good Aristotelian. Liceti was politely incredulous – and he felt confident that the rest of the world would share his...

    • 8 The Leaning Tower
      (pp. 36-42)

      In the autumn of 1589 Galileo became a professor of mathematics at the University of Pisa. He had taken the first step on the road to a professional career and to financial security. But there should be no illusions about his situation: his annual salary was sixty florins, significantly less than the income of a good stonemason.¹ It was not possible to live as a gentleman on such an income. There were professors of philosophy in prestigious institutions who were earning fifteen times as much; Galileo’s own friend Jacopo Mazzoni was earning seven hundred florins at Pisa.² And this was...

    • 9 Inertia
      (pp. 43-45)

      We have now looked at Galileo’s core argument inOn Motion. It is an argument that models itself on Archimedes (and openly declares itself to be in opposition to the ridiculous arguments of the Aristotelians) but one that any competent Aristotelian could have followed. From an Aristotelian point of view it contains two major departures from anything resembling orthodoxy: the denial of lightness, or the insistence that everything has weight; and the possibility of movement in a vacuum. But there is a further argument inOn Motionwhich is striking and which contemporary Aristotelians would have found profoundly puzzling.


    • 10 Nudism
      (pp. 46-48)

      Galileo does not seem to have been a success in his first job. Not only was his salary low, but it was reduced by fines for missing lectures and for failing to wear the required academic dress, the toga, a sort of cassock or academic gown (which can be clearly seen in every portrait of Galileo). His initial appointment was for three years, and at the end of it he faced unemployment. According to Viviani he had made a powerful enemy, and knew he was unlikely to have his contract extended. On 2 July 1591 Galileo’s father died, but Galileo...

  8. Part two: The watcher of the skies

    • 11 Copernicanism
      (pp. 51-66)

      The years 1592 to 1610, during which Galileo taught at the University of Padua, are undoubtedly the most important in his life as a scientist. During this time (the best years of his life, he would say later) he made all his major discoveries in physics, while the two great last works, theDialogueand theTwo New Sciences, are in large part polished presentations of work undertaken during this same early period.² Yet the record that survives from this period is thin, even meagre: one great book, or rather pamphlet,The Starry Messenger, published in 1610; a privately printed...

    • 12 Money
      (pp. 67-69)

      Between 1591, when his father died, and 1610 Galileo was engaged in a constant struggle to make ends meet. It seems likely that his sister Virginia married in 1591 on terms negotiated by his father. Galileo inherited the obligation of paying for her dowry, and in 1593 Benedetto Landucci, his brother-in-law, was threatening to have him arrested if he came to Florence.¹ Galileo borrowed two hundred ducats in an effort to sort things out.²

      In 1601 the marriage contract for his sister Livia provided for a dowry of 1,800 ducats, to be paid over a period of five years by...

    • 13 Fields of fire
      (pp. 70-75)

      When Galileo arrived in Padua there was, some maintain, a major reorientation in his intellectual interests.¹On Motionis a purely philosophical work; by contrast his very first surviving letter from Padua is concerned with a practical problem in naval technology: how long should the oars of a galley be? There could be no more basic question in Mediterranean naval warfare in the period, for fighting was entirely conducted, as in the classical era, by boats powered, not by the wind (there were too many calm days), but by the bodies of human beings – usually convicted criminals condemned to the...

    • 14 The experimental method
      (pp. 76-86)

      Was Galileo an experimental scientist? Few subjects in the history of science are more contested. There are a number of possible sources of confusion to be resolved before proceeding. First, what is an experiment? In modern usage, the idea of an experiment involves the reproduction of some naturally occurring phenomenon in a carefully controlled and therefore artificial setting – what Kant called reason proceeding ‘after a plan of its own’. We might distinguish between an experiment, which is designed to play a part within an argument, perhaps even to test a hypothesis, and an experience: I have plenty of experience of...

    • 15 The telescope
      (pp. 87-92)

      In the autumn of 1604 a new star appeared in the sky. News of it spread rapidly amongst those interested in astronomy. Thirty years earlier, in 1572, Tycho Brahe had turned a new star into acause célèbre. According to the philosophers, the heavens were unchanging, eternal, perfect. There could be no change in the heavens, and any change that did take place must occur in the vicinity of the earth – in the sublunary world. In their view, consequently, the choice was simple: either the new star had always been there, or it was not a star at all, but...

    • 16 Mother
      (pp. 93-95)

      In November 1609, Galileo’s mother, Giulia Ammannati, wrote a letter from Florence to one of Galileo’s domestic servants, Alessandro Piersanti.¹ In it she expresses concern that she has heard nothing from him for several weeks, and reassures him that his letters to her will not be intercepted. She wants him to collect some cloth from the weaver’s – and it is important that no one from Galileo’s household catches sight of it. She has strong views on what should be done with Galileo’s eldest daughter, Virginia; unfortunately Piersanti already knows what they are, so she does not repeat them for our...

    • 17 The Starry Messenger
      (pp. 96-105)

      In Venice there are approximately sixteen hours of daylight in June and July, and only eight in December and January. In the autumn of 1609, as the days shortened, Galileo turned his improved telescope on the heavens. He mounted it on some sort of stand, but he still had to learn to slow his breathing; even his pulse seemed to shake the telescope; and as the evening temperature dropped the glasses kept misting up. Early in January 1610 he discovered he could reduce the halo around objects by fitting a circle of masking material with an oval hole in it...

    • 18 Florence and buoyancy
      (pp. 106-113)

      Galileo’s interests and those of the Medici were even more firmly tied together when, in May of 1610, Galileo agreed to move to Florence, to take up the world’s first research professorship there. In the course of his life Galileo made two momentous decisions, decisions which were to determine everything that happened afterwards. This move was the first; the second came in 1632. Why would Galileo leave Venice? Not to improve his finances, for his salary in Florence was roughly the same as the salary he had been promised in Venice, and he gave up the revenue from private teaching....

    • 19 Jesuits and the new astronomy
      (pp. 114-124)

      The publication ofThe Starry Messengerin March 1610 was followed by a carefully managed campaign to win acceptance for Galileo’s discoveries, which were so far at odds with everything that went before that they at first met with considerable scepticism. That campaign depended on mobilising the resources of the Medici government, for the honour of the Medici was now linked to the success of Galileo’s publication.

      But Sarpi, Sagredo, Cremonini and Galileo’s other Venetian friends would have been astonished if they had seen the first letter (or at least the first surviving letter) that Galileo wrote on arriving in...

    • 20 Sunspots
      (pp. 125-131)

      Sunspots can sometimes be seen with the naked eye: in 1590, for example, an English ship’s captain, off the coast of West Africa, saw a spot ‘about the bignesse of a shilling’ on the sun. Johannes Kepler saw a spot in 1607, when looking at the sun through cracks between the shingles in the loft of his house in order to observe a transit of Mercury; at the time he thought it was Mercury, but with hindsight he realised it was a sunspot.¹ A similar spot had been seen in Florence in 1604.²

      Galileo was probably the first to see...

    • 21 The Catholic scientist
      (pp. 132-134)

      From the summer of 1611 to the winter of 1612–13 Galileo was pursuing a strategy. He compares his opponents to soldiers defending a fortress who rush to repulse an attack, leaving the rest of the castle undefended – and we must assume that he was every bit as careful in planning his attacks as he thought his adversaries were careless in their responses.¹ Historians have lost sight of that strategy because it is directly at odds with the strategy he was to pursue from 1613 to the end of his life. Galileo is famous for arguing that religion and science...

  9. Part three: The eagle and the arrow

    • 22 Copernicus condemned
      (pp. 137-156)

      The first indication that Galileo’s position might be deteriorating rather than improving came on the morning of 12 December 1613.¹ Benedetto Castelli had breakfast with the grand duke, the duchess, and the grand duke’s mother, Christina of Lorraine, who were on one of their periodic visits to Pisa. Also present, amongst others, was a Pisan Aristotelian philosopher, Cosmo Boscaglia. Castelli, as one might expect, had spoken in praise of Galileo’s latest scientific discoveries; Boscaglia had conceded that Galileo’s telescopic discoveries were indeed to be trusted, but he had rejected the idea of a moving earth, which he said was contrary...

    • 23 Comets
      (pp. 157-170)

      In 1617 Galileo made a last attempt to find a proof for Copernicanism that no one could question: he tried, yet again, to measure the parallax of fixed stars to see if their relative position changed over time.¹ But he was no more successful than those who had tried before him. He was also preoccupied with his schemes for determining longitude by reference to the eclipses of Jupiter’s satellites. Then between August and November 1618, three comets appeared in the sky. All three were visible to the naked eye, the last to appear being ‘of such brightness that all eyes...

    • 24 The death of Gianfrancesco Sagredo
      (pp. 171-175)

      Sometime in 1621 or 1622 Galileo spent thirteen days lost in conversation with Diodati. With a foreigner and a Protestant he could speak freely, as once he would have spoken to Sarpi and Sagredo in Venice. Briefly, in the garden of his Florentine villa, Galileo relived the liberty he had experienced in Padua. For now, after the death of his friend Salviati in 1614 and the condemnation of Copernicanism in 1616, Galileo was increasingly isolated. He had to be careful not only about what he wrote, but about to whom he spoke and what he said. Above all, he had...

    • 25 Urban VIII
      (pp. 176-181)

      Just when Galileo was feeling lonely and isolated, Maffeo Barberini, a Florentine, was elected pope on 6 August 1623, taking the name Urban VIII. He and Galileo had been on friendly terms since 1611, when Barberini had supported Galileo in a debate, conducted over the grand duke’s dinner table, about why bodies float or sink. He praised Galileo in a poem he wrote in 1620, a copy of which he sent to Galileo accompanied by a letter signed ‘your brother’. As soon as he was elected he promoted two friends of Galileo’s, fellow Linceans and fellow Florentines, Virginio Cesarini (who...

    • 26 Family ties
      (pp. 182-190)

      Amongst professional historians, biography is not an intellectually respectable genre. This is because there is a good deal of confusion about what biography is for, and – if we are honest – just as much confusion about what history is for. As we turn to take a closer look at Galileo’s private life we need to sort out some of these confusions.

      My primary purpose in this book is to provide an intellectual biography of one of the world’s greatest scientists – to reconstruct the development of his ideas over time. The obvious objection to such an enterprise is that people do not...

    • 27 Permission to publish
      (pp. 191-200)

      In March of 1629 Galileo fell seriously ill. He came face to face with his own mortality. And he resolved that come what might he would at last finish theDialogue.¹ His friends were delighted. It was high time, one of them had recently written to him, that he stopped murdering himself with his stubbornness, stopped betraying his intellectual gifts, and recognised his responsibility to posterity.² Within a few weeks he was once more well enough to work in his garden, but he was not yet ready to pick up his pen.

      Finally in October 1629 he announced that he...

    • 28 Alessandra Buonamici
      (pp. 201-202)

      In 1630, when Galileo was in Rome seeking permission to publish theDialogue, he heard of the unexpected appearance in Florence of Alessandra Buonamici, the sister of his daughter-in-law Sestilia Bocchineri. In 1623, when in her late twenties, a widow employed as lady-in-waiting to the empress at the Viennese court, Alessandra had married for the third time. Her new husband, the Florentine Giovanfrancesco Buonamici, had soon departed on a mission to Spain; now he was back in Florence and Alessandra had travelled from Vienna to Florence, through war and plague, in only eighteen days. Galileo, who never went anywhere if...

    • 29 A river floods
      (pp. 203-205)

      In 1630 Galileo was already at work on his next book. But he also had to deal with a minor distraction. In December, in his capacity as the grand duke’s mathematician, he was invited to express an opinion on a debate that had divided Florence’s ruling establishment. The problem was the river Bisenzio, which meanders across the plain that stretches northwest from Florence. The Bisenzio had flooded during the previous autumn, and since many of Florence’s wealthiest families owned land along its banks, and since the local landowners would pay the cost of the works required to prevent future flooding,...

    • 30 Publication
      (pp. 206-207)

      Galileo certainly had more important things to worry about. The wife of the Florentine ambassador in Rome – who was a good friend of Galileo’s, and who could not be thought to represent the Florentine government – entered into negotiations with Father Monster on Galileo’s behalf. At first Riccardi demanded that the final text of the book be sent to him, but then he agreed to sign off on the book on two conditions: he must see the beginning and the end, and the book must be reviewed in its entirety by a censor in Florence. He was happy for Galileo to...

    • 31 The Dialogue
      (pp. 208-212)

      Galileo’sDialoguecontains one major new argument, on the subject of sunspots. When the book appeared in February 1632 Galileo’s Jesuit opponent Scheiner was convinced that this section had been based on material lifted without acknowledgement from his ownOrsini’s Rose(1630, named in honour of Scheiner’s patron, Paulo Giordano Orsini), although we know (as Scheiner could not) that Galileo had not seen Scheiner’s book until his own was well on its way through the press.¹ Valiant efforts have been made to find an innocent explanation for the close match between various details in Scheiner’s account and in Galileo’s. It...

  10. Part four: Prisoner to the Inquisition

    • 32 Maria Celeste and Arcetri
      (pp. 215-217)

      In the autumn of 1631, with his book finally cleared for publication, Galileo moved house. Since 1617 he had lived in a magnificent villa called Bellosguardo a couple of miles to the west of Florence. But now he was getting old, and he was going blind. He needed to think about a time when he would no longer be able to get about easily. What worried him most was that he would be cut off from his daughters who were in a convent in Arcetri, about an hour’s walk away. He moved to be as near to them as possible....

    • 33 Trial
      (pp. 218-228)

      Publication of Galileo’s book was completed on 21 February 1632, but the measures taken to prevent the spread of the plague meant that by the end of May only two copies had arrived in Rome, one of which was in Castelli’s hands (although it had been presented to Francesco Barberini) and the other probably in Riccardi’s.¹ It was not until July that six more copies arrived, three of which were given to Galileo’s close friends and supporters. Within days the authorities were trying to seize every copy in Rome and the book had been referred to a special commission of...

    • 34 The Two New Sciences
      (pp. 229-234)

      Within a few weeks of Galileo’s arrival in Siena work began on a Latin translation of theDialogue,which was eventually published in Strasbourg in 1635. The project originated with Élie Diodati, a French Protestant who had long been a friend of Galileo’s, and he recruited Matthias Bernegger, a German Protestant who had earlier translated Galileo’s book on the sector into Latin. Bernegger repeatedly claimed that he had been invited by Galileo himself to undertake the translation, and it used to be argued that Galileo had contacted Diodati as soon as he arrived in Siena to ask him to ensure...

    • 35 Vincenzo, son of Galileo
      (pp. 235-239)

      Vincenzo Galilei was born on 21 August 1606. He was four when Galileo moved to Florence, and naturally he stayed behind with his mother, Marina Gamba. When she died in 1612, Galileo made temporary arrangements for his care and then brought him to Florence.¹ In June 1619 he arranged for him to be officially made legitimate (although without entitlement to all the rights of citizenship), which opened the way for him to obtain an education at the University of Pisa: he graduated with a doctorate in law in 1628.² It was, unfortunately, a popular saying that a Pisan doctorate was...

    • 36 Galileo’s (un)belief
      (pp. 240-250)

      This chapter presents a radically new account of Galileo’s religious views, developing a line of argument previously touched on in chapters 16 and 22. Let me make clear, to begin with, that I do not think it is possible to answer the question whether Galileo was a believing Catholic in any straightforward way. Throughout his life he claimed to be a good Catholic, but then the consequences for him if he had failed to do so would have been extremely serious. The case of Mme de Warens is instructive: she was paid a pension because she had converted from Protestantism...

    • 37 The cosmography of the self
      (pp. 251-258)

      Galileo was the first modern scientist, arguably the first true scientist. He constructed a new generation of instruments to be used for scientific purposes: he invented the thermometer, the micrometer and the first accurate timepiece, the pendulum clock, and he transformed the telescope and the microscope from toys into tools for the discovery of invisible worlds.¹ Galileo’s ambition was to be a new Archimedes, but almost by accident he came across a new way of learning about nature, the experimental method, and as a result invented what we now call science. Before he could invent science he had to devise...

  11. Coda: Galileo, history and the historians
    (pp. 259-267)

    Galileo died quietly on 8 January 1642. He was seventy-seven. As soon as the news reached Rome instructions were sent that there was to be no tombstone, or any memorial within a church. (Viviani ended up turning the front of his house into a private memorial to Galileo, and left money in his will for a fine tomb.) A modest plaque was permitted in 1673, and a proper tomb finally allowed in 1737. (When Galileo’s tomb was opened to move his body to its new location, the body of an unknown woman was found buried – perhaps reburied in 1674 – with...

  12. Notes
    (pp. 268-307)
  13. Bibliography
    (pp. 308-319)
  14. Index
    (pp. 320-328)