GALILEI, GALILEO. - Born on 15 Feb. 1564 in Pisa to Vincenzo, a Florentine, and Giulia degli Ammannati of Pescia; in his boyhood he was with the Vallombrosan monks; he then enrolled at Pisa in the Faculty of Arts, and around the age of twenty he applied himself with particular study to mathematics. The environment at Pisa was peripatetic par excellence, but this did not deter the young scholar from proceeding on his own account, grounded in the study of Archimedes and in experience. In 1587 he was in Rome, where he entered into relations with Fr. Cristoforo Klau (Clavius), master of mathematics at the Roman College (d. 1612), with whom he thereafter always remained on excellent terms. In 1588 he tried in vain to be appointed to the teaching of mathematics at the Studio of Bologna; in July 1589 he obtained instead the chair at that of Pisa; and not having been reconfirmed in it, he moved to that of Padua, granted to him by decree of the Senate of Venice on 26 Sept. 1592. The Padua years were truly decisive for G.'s scientific career and an incentive to intense activity. Besides giving the public lectures, as was his duty, he gave private lessons and kept a boarding house for students; he organized a workshop of precision instruments: compasses, magnetic compasses, quadrants, set squares, etc., and later also lenses and spyglasses; he made friends among the Venetian nobles and had illustrious disciples, among them Gian Francesco Sagredo, the monk Benedetto Castelli, and the canon Paolo Aproino. In these years, from a relationship with a certain Marina Andrea Gamba, he had Virginia (later, in religion, Maria Celeste), Livia (later, in religion, Angelica) and Vincenzo Andrea, whom he would later take with him to Florence. With the precise aim of making science popular, he began his career as a publicist, making use of the vernacular tongue, in the use of which he always succeeded with admirable clarity, precision and brevity, keeping well away from useless citations and from any rhetorical emphasis, thereby making himself a tenacious opponent of the corruption of his time.
From this first period date a Treatise on the Sphere, a Treatise on Fortification, some manuscripts of a practical character On Mechanics, a pamphlet on the Compass of Proportion (1606) which illustrated an instrument he had built to speed up calculations. By 1597 he was already a convinced Copernican and was in correspondence with Kepler on the subject, but he could not profess it publicly; above all he devoted himself to refining his scientific method, for the constant application of which G. can be called the father of modern science. From the very beginning he set out to follow the method taught by mathematicians, that is, «to make what is said depend on what has been said, without ever assuming as true what must be explained»; whereas according to the methods then current «those who learn never know things from their causes, but believe them only by faith, that is, because Aristotle has said them. And whether what Aristotle has said is true, few are those who investigate; it is enough for them to be held learned because they have in hand a greater number of Aristotelian texts» (Opere, national ed., I, p. 285). The rational interpretation of phenomena, together with the investigation of their mutual dependencies through, as far as possible, mathematical deductions, finds in G. its first conscious and complete expression: «I truly believe that the book of philosophy (taken in the broadest sense of natural philosophy) is that which perpetually lies open before our eyes; but because it is written in characters different from those of our alphabet, it cannot be read by everyone: and the characters of such a book are triangles, squares, circles, spheres, pyramids and other mathematical figures most suited to such reading» (ibid., XVIII, p. 293). Here, if on the one hand G. reveals in mathematics his preference for geometry, on the other he insists on direct experience, to which the speculations of the ancients can indeed lend aid, provided however that they are not in contrast with what direct experience teaches. Of an experimental method understood in this sense G. would be an incomparable master to famous disciples, and this new school would completely renew the study of nature.
G.'s investigation was directed from the beginning toward different fields. Already in 1602 he was occupied with magnets, which he manufactured, increasing their power of attraction; at the same time he was studying the phenomena of heat, on which his disciple Sagredo worked; hydraulic problems were not foreign to him. But the problems relating to motion and gravity were those that particularly kept his activity occupied throughout his scientific life. Indeed he was already attending to them at Pisa, where he also observed the isochronism of the small oscillations of the pendulum and where he began to draft his notebooks «de motu gravium» and engaged in the struggle against the Aristotelians bound to the erroneous conclusions of the master; at Padua he was already occupied «with the wonderful problem of the pendulum», with the fall of projectiles; subjects that would later be for him matter of broader developments. Astronomical problems too were connected with those of motion, but G. made them an object of study only at a later time; on the comet of Oct. 1604, which he also observed, he left no scientific treatment.
The second period came with 1609, which carried G. into a broader field of activity and celebrity. The vague report that a spectacle-maker in the Low Countries had with lenses built an instrument with which one could see distant things close at hand, induced G. to build one in his laboratory (Aug. 1609) and he immediately showed it at Venice; he then built many, and for a long time no one equaled him in perfection. It is known that he later adapted this telescope to see the smallest things, but this did not much interest the inventor; who instead pointed his instrument toward the sky. This was in Jan. 1610 and he immediately observed the lunar spots, the immense multitude of fixed stars particularly in the Milky Way and their difference from the planets, the existence of the satellites of Jupiter. He gave news of this to the world in the Sidereus nuncius, which came off the presses at Venice in March, written precisely in Latin to make it accessible to all of Europe. The Nuncius came to overturn all the cosmological conceptions then in vogue and completely upset so-called judicial astrology, which was always in fashion; it therefore met from the beginning with open incredulity in the scientific world: the truthfulness of the telescope was doubted, as were the accuracy and the interpretation of the observations. Certainly few could dispose of a good telescope to repeat the observations, others out of prejudice did not want to use it, such as Cesare Cremonino, G.'s colleague at Padua. In Germany, on the other hand, Kepler was for G., especially when he could use a good telescope, and so too were Fr. Clavius and Fr. Tommaso Campanella.
The celebrity that G. had by now acquired among the truly learned moved Grand Duke Cosimo II to want him again in Tuscany, and on 10 June 1610 he named him first mathematician of the Studio of Pisa and grand-ducal mathematician and philosopher, without any obligation to teach. G. accepted, and on 12 Sept. he was at Florence, where he also moved his laboratory. Here he continued the observations on the singular conformation of Saturn, begun at Padua (25 July), and in Sept.-Oct. 1610 he became convinced of the phases of Venus analogous to those of the moon, a sign that this planet revolved around the sun from which it received its light. The Ptolemaic system was thus completely refuted, but the Peripatetics did not show that they noticed.
In Feb. 1611 he made a journey to Rome, where he also had occasion to discuss the sunspots he had observed first; he was very well received by Clavius and by the Jesuits of the Roman College; by Federico Cesi, Marquis of Monticelli, he was enrolled in his Accademia dei Lincei and G. held himself greatly honored by it; he received honorable welcomes also in the Roman ecclesiastical world, which wished to satisfy itself of his discoveries. In May 1612 he published at Florence, at the invitation of the grand duke, his conclusions on floating bodies, following the doctrines of Archimedes and arousing a lively polemic from the irreconcilable Peripatetics. Who received from him another blow with the three letters that in the second half of that that year he wrote to Marco Welser of Augsburg communicating his further observations on the sunspots in refutation of the letters that Fr. Scheiner, a Jesuit, had sent on the same subject. They were printed in 1613 under the care of the Lincei in Rome.
In the following years the controversy flared up concerning the acceptability of the heliocentric doctrine with regard to the Faith. G. spread that theory in oral discussions and in epistolary correspondence; but, with few exceptions, he found arrayed "against himself the universal opinion, imbibed, one might say, ab orbe condito." To some, even learned men, it seemed that the system of Tycho Brahe was sufficient to reconcile the new discoveries with religious tradition. It was, moreover, a widely established custom to introduce into discussions, even purely philosophical ones, authorities from Scripture and the Fathers, and this was not neglected in the heliocentric question either, in order to condemn it as contrary to the Faith and heretical. In Dec. 1613 Fr. Castelli ahad upheld a discussion on the matter at Pisa before the court of Tuscany and had given an account of it to G. The latter took up the subject again in a long letter to Castelli dated 21 Dec., which was quickly circulated, showing how ill-advisedly those who brought Scripture into such matters proceeded and how little force the proofs they claimed to draw from it had. With a properly theological intent, however, Father Paolo Antonio Foscarini, a Carmelite (d. in June 1616), entered the field at Naples at the beginning of 1615 with a letter in which, after praising G., he showed very well how the scriptural and patristic passages against the heliocentric doctrine were quite incongruously adduced and admitted of a different interpretation. G. learned of this letter, which was soon printed, and took heart in that same year to address to Maria Cristina, the Grand Duke's mother, a letter truly admirable for its clarity and precision, theological included, in which he developed the arguments already touched upon in the letter to Castelli and in others; and, having shown the relations between science and Faith, he in turn refuted the opposing arguments. It was not he who had brought the discussion into the scriptural field, but he was driven there by the necessity of safeguarding his position as a scientist and a believer. This letter was not printed at the time; but it was circulated in copies in the cultured circles of Tuscany.
(Ist. Alinari)
On 7 Feb. 1615 Father Niccolò Lorini, a Dominican, had sent from Florence to Cardinal Paolo Sfondrati, prefect of the Congregation of the Index, a copy of G.'s letter to Father Castelli as containing «many propositions or matter for suspicion of temerity». Since the letter was not printed, the cardinal transmitted it to Cardinal Mellini, secretary of the Holy Office, where it was promptly taken under examination. On 20 March Father Tommaso Caccini, also a Dominican, presented a formal denunciation to the Holy Office against G., and a judicial inquiry was therefore begun at Florence. Realizing that the Florentine enmities would not fail to have repercussions at Rome, G. decided to go there without further delay. He hoped to win over to his side the most cultured elements of the city, and he took no account of the warning of his friends that «the Peripatetics were very powerful there». Many of the illustrious personages who, even in the Curia, were on his side did not look favorably on his going about parading himself as a convinced supporter of the Copernican doctrines; while appreciating his studies and his discoveries, they did not intend to follow him along that path. In the ardor of his convictions G. failed to realize what a difficult thing it was to cloak a philosophical construction taught as unassailable in all the ecclesiastical and secular schools, and how hard a thing it must have appeared to those masters to renounce doctrines taught and held for many years with full conviction. Having left Florence with the Grand Duke's permission, G. arrived in Rome on 11 Dec. 1615, a guest of the grand ducal ambassador on the Pincio, and he immediately set about busying himself greatly, disputing about his theories with the most prominent personages, even with Father Caccini, also putting his arguments in writing and consequently arousing against himself the aversion of the followers of the old systems, who made of it outright a question of religious orthodoxy. All this led to the necessary consequence that it was fitting to clarify the relations between the Copernican theory and Christian tradition, and thus officially to bring the discussion from the personal field to the strictly doctrinal one. It was therefore easy for G.'s adversaries to persuade the Holy Office of the necessity of a decision that would remove all uncertainty. The Holy Office referred the examination to a commission of eleven theologians who on 24 Feb. 1616 replied to the two questions put to them: 1) «that the sun is at the center of the world and immovable from local motion; is a proposition absurd and false in philosophy and formally heretical, because it is expressly contrary to Holy Scripture»; 2) «that the earth is not the center of the world nor immovable, but moves according to itself also with diurnal motion; is likewise a proposition absurd and false in philosophy and, considered theologically, is at least erroneous in the Faith». This reply of the theologians was ratified the next day by the cardinals of the Inquisition, in the presence of the Pope; but it was not given official publication as an act of the Holy Congregation and remained as an internal rule, as the conclusion of men learned and qualified in the matter.
As for G., who had publicly compromised himself with his discussions, it was decided to proceed in his regard in a benign form, and the task was entrusted to Cardinal Bellarmino to admonish him officially to desist from championing such theories, with the threat, in case of disobedience, of being imprisoned. On 26 Feb. the cardinal carried out the task in the presence of the commissioner of the Holy Office and of some witnesses. G. promised to obey, undertaking «in no way to hold, teach or defend orally or in writing» heliocentric doctrines. For its part, the Holy Congregation of the Index on 5 March prohibited Father Foscarini's book together with all others, not listed, that upheld the same doctrines, and decided that in new printings of Copernicus's work a few phrases should be corrected so that it would appear that he had proposed the heliocentric system as a simple astronomical hypothesis. Since a rumor was spreading that G. had been obliged to make a formal abjuration, he took care to have Cardinal Bellarmino issue him on 26 May a certificate of the communication made to him regarding the Copernican theory. Thus ended what was improperly called G.'s first trial. At the beginning of June he returned to Florence, more determined than ever to work in the best and most prudent of ways for the triumph of his doctrines by demonstrating for the time being the inconsistency of the opposing doctrines.
1618 was the year of the comets: three appeared, of which the last (Nov.-Jan. 1619) aroused particular interest among astronomers and the public; there was discussion above all about their nature: whether they were true planets or merely meteors. G.'s judgment was awaited, but he was ill and could not make direct observations. It was instead Father Orazio Grassi, astronomer of the Collegio Romano, who printed a public disputation: De tribus cometis, and G. seized upon the examination of this publication, bringing his friend Mario Guiducci into the foreground in a discourse delivered at the Accademia Fiorentina. More than to establish a doctrine, the lecture was directed at demonstrating the untenability of the theories of Grassi and of other astronomers, including Tycho Brahe, lamenting that, instead of direct observations, they reasoned solely on the basis of preconceived theories. Fr. Grassi replied under the guise of a supposed disciple in defense of the master's doctrine, and under the name Lonio Sarsi Sigensano published at Perugia the Libro astronomico ac philosophico (1619) in confutation of Guiducci. G.'s friends agreed that a reply was necessary, and in Oct. 1623 he published the Saggiatore, in which, in 52 chapters, he examined all of Sarsi's assertions. A polemical work, not a properly systematic treatise, in which the author is careful not to present himself as a defender of the Copernican theory, though insinuating here and there its superiority, it destroys Sarsi's assertions and his objections to Guiducci's discourse and points out that in scientific research, more than to the opinions of authors, one must have recourse to the direct observation of phenomena and to mathematics; for this reason he avoids citing Holy Scripture as was unfortunately done. The book, addressed to the young Roman patrician Virginio Cesarini and dedicated to the new pope Urban VIII, had wide circulation, provoking a counter-reply on the part of Fr. Sarsi. Confiding in the benevolence that Urban VIII had shown him years earlier, G. in the autumn of 1624 undertook a new journey to Rome; he was promised ecclesiastical benefices, but as regards the acceptance of his ideas he met only with disappointments; so that, almost by way of excuse, refuting his adversaries, he wrote that he did not intend by this to uphold the Copernican doctrines, but to make known to heretics that, although he could not accept them, the arguments on which they were founded were not unknown.
Meanwhile a new proof presented itself to G.'s investigation in favor of heliocentrism: that of the ebb and flow of the sea. He would have nothing to do with the influence of the stars, almost as a reaction to what was one of the cornerstones of the astrology of the time; therefore he thought that the influence of the sun and moon had nothing to do with the cause of the tides; according to him they were due to the rotation of the earth. He wished to frame this new supposed argument in a broader treatment that would examine the two greatest cosmological systems: the Ptolemaic and the Copernican; he set to work on it in the autumn of 1624, but only in Oct. 1629 did he attend to it with the intention of carrying the work through to the end. It is conceived as a dialogue divided into four days with three interlocutors: Filippo Salviati, who upholds the Copernican side, repeatedly professing however to reason as on a scientific hypothesis that the Faith does not accept; Gian Francesco Sagredo, who plays the part of the listener, cultured but lay, who repeats the arguments, tightening them; the third is Simplicio, the traditionalist, neither ignorant nor foolish, always attached to the doctors and to books, without contact with nature and with experiment, who, not without caricatural touches, defends the current ideas. They dispute about the nature of the heavens, about the diurnal motion of the earth and its motion around the sun, about the ebb and flow of the sea and the fall of heavy bodies.
The work was to be printed at Rome and Prince Federico Cesi, head of the Accademia dei Lincei, was to see to it; therefore in May 1630 G. went to Rome and
entered into relations with Fr. Niccolò Riccardi, master of the Sacred Palace, to obtain from him the license for printing. The rule imposed was that the heliocentric system be set forth as a pure mathematical hypothesis, and because in the text it was not so, the work had to be reduced to a hypothetical form, with a chapter and a peroration to that effect, and even the body of the treatment had to undergo some revisions; after this Fr. Riccardi reserved to himself the right to review the whole. In any case the first examination turned out favorably. On Aug. 1, 1630, Cesi died and G. decided that the printing should be done at Florence with a dedication to the grand duke; but owing to Fr. Riccardi's long hesitations it was not finished until Feb. 1632 and it came out with the imprimatur of the vicegerent of Rome, of the master of the Sacred Palaces, of the Inquisitor of Florence, of the vicar general of Florence and of the grand-ducal government.
The book was widely circulated from Feb. 1632 and also reached Rome, where its content was not liked and in July an attempt was made to prevent its circulation there; the Pope willed in this regard that matters be pursued to the bottom and that the Holy Office deal with it without further ado; and indeed a commission was charged with the examination. It soon became a common conviction that, despite appearances, the author was defending the Copernican theory as true; it was noted that the preface sent by Fr. Riccardi from Rome was printed in a different typeface, almost as if extraneous to the rest, and that authors venerated in the Church were being manhandled. And to one who proposed that it be corrected, the Pope replied that it would have been necessary to redo the whole book from scratch. The decisions did not take long to follow. On Sept. 23, 1632, Urban VIII had the Inquisitor of Florence commanded to intimate to G. in legal form to appear before the Roman Inquisition within Oct. G.'s delays, which he attributed to his poor state of health, were regarded as evasions and recourse was had to threats; the original manuscript was demanded and all printed copies were ordered withdrawn. Since the Pope did not intend to yield, even the grand duke urged G. to obey. The latter left
Florence on Jan. 20, 1633, arrived in Rome on Feb. 12 and presented himself before the tribunal. He was granted lodging with the ambassador of Tuscany, Nicolini, at the Pincio, with the obligation to live in retirement. Only on Apr. 12 was he obliged to enter the palace of the Holy Office, where the only three available rooms were assigned to him, without locks, with freedom to go down into the courtyard, to keep a servant and to receive food from the embassy. The interrogation began at once. G. had hoped to be allowed to defend his theories, but this was not the practice of the tribunal, for which they had already been qualified since 1616, and indeed the first question of the commissary Fr. Vincenzo Macolano concerned the precept given him at that time by Card. Bellarmine; G. admitted that he was the author of the Dialogue, adding that he had not "in the said book either held or defended the opinion of the mobility of the earth and the stability of the sun." On this denial G. tried to base his defense, while, as the commissary rightly noted, the contrary "appears manifestly in the book composed by him." To spare him measures of rigor the commissary obtained leave to treat with him extrajudicially, and on Apr. 20 induced him to admit that he had gone too far in his book in favor of the Copernican doctrines, and in the second interrogation of Apr. 30 he admitted that "the arguments brought for the false (Copernican) side, which he intended to confute, were set forth in such a way that by their efficacy they were more powerful to constrain than easy to be dissolved," and declared himself ready to write in the opposite sense and to add for that purpose one or two days to his dialogue. After this second interrogation G. was at once again granted, for reasons of health, to remain "in a prison locus" in the palace of the ambassador Nicolini, always holding himself at the disposal of the Holy Office.
On the third summons before the Holy Office, on 10 May, regarding the precept issued to him in 1616, G. insisted on asserting "that he had not knowingly and willingly transgressed the commandments given him" at that time, and as for the Dialogue he did nothing but refer to what he had said in the first interrogation. He perhaps hoped to avoid a formal abjuration, but it was clear that his assertions were not true. After this the Pope, on 16 June, communicated his decisions: G. was now to be interrogated without further ado on what he really thought (super intentionem), with the threat of torture as well; and if he persisted, he was to make the abjuration and be condemned to imprisonment at the discretion of the Congregation, with an injunction no longer to treat the Copernican doctrine in any way under penalty of being treated as a "relapsus"; the Dialogue was to be prohibited and the sentence made public, transmitted to the nuncios and inquisitors in the various countries and especially to Florence. The interrogation "super intentionem" took place before the father commissary on 21 June, and G. again maintained that before 1616 he had been indifferent between the two great systems, but that afterward he had no longer defended the Copernican system. And when the threat of torture was made to him, he replied that he was there to render obedience, again insisting on his denial regarding the Copernican system. The threat was merely a procedural element, nor could it, according to the rule, have been inflicted on him, old and ill as he was; in fact "he was sent back to his place," and the next day in the convent of the Minerva, before the cardinals and prelates of the Congregation, the sentence was read to him; in it, while holding that G. had not fully told the truth, it was acknowledged that under rigorous examination he had answered in a Catholic manner; in any case he had rendered himself "vehementer suspectum de haeresi," incurring the censures and penalties relating thereto; from these, after the abjuration, he was absolved; the Dialogue was prohibited and the author condemned to imprisonment of the Holy Office at the discretion of the Congregation, with the obligation of reciting the seven penitential psalms once a week for three years. G. made the abjuration according to the prescribed formula, accepting the obligations imposed on him. Such was the trial of G., for which, without reopening the doctrinal decision of 1616 concerning the unacceptability in the religious field of the Copernican system, G. was judged and condemned on the fact of his continued adherence to it, demonstrated above all by the Dialogue on the Two Chief World Systems. By now he was a prisoner of the Holy Office; however, as his prison he was assigned the Palazzo dell'oratore on the Pincio; on 30 June he had as a favor the opportunity to stay at Siena with that archbishop Ascanio Piccolomini; then on 1 December he received permission to retire to his villa del Gioiello near S. Matteo d'Arcei, which he had bought on 27 September 1631, and there he remained, as a prisoner, until his death. Indeed, every attempt to obtain a complete pardon for him was in vain: Urban VIII would not hear of it. The last years of G. were troubled by wearisome illnesses, in which he lacked the comfort of his daughter Sister Maria Celeste, who died on 2 April 1634; in December 1637 he became completely blind. He was particularly displeased by the prohibition of printing for all his works. Nevertheless he never interrupted his studies, particularly on "motion and resistances," as he himself wrote on 12 July 1636, and from them he formed a volume printed by the Elzevirs at Leiden in 1638, which was immediately sold even in Rome: Discourses and Mathematical Demonstrations concerning Two New Sciences pertaining to Mechanics and Local Motions. The work is in four dialogues with the same interlocutors as the Two Chief World Systems, of which it is, as it were, a continuation, maintaining a tone no longer polemical but serene and calm. Taking up again his youthful writings De motu, he lays the foundations of dynamics, and opposing to Aristotle the law of inertia, he gives the first rational basis to the Copernican system and the sure foundation to Newton's principle of universal gravitation. But G. was still pursuing other developments of his doctrines, which his pupil Vincenzo Viviani, with the notes he had collected, later set out in two further days added to the New Sciences.
And since the States General of the Netherlands had announced a competition to solve the problem of determining longitude during navigation, G. took up again the hypothesis whether this could not be achieved by making use of the observation of the eclipses of Jupiter's satellites with the help of a good telescope and a clock. In this connection he had been in long correspondence with Spain after 1616, without any success; and also this time (1636-40), because of technical difficulties, he reached no other conclusion than to receive as a gift a gold chain (1638), which he refused so as not to create new suspicions. He continued to the very last in the examination of his favorite problems, and his last letters deal with the libration and the lunar candor, until he piously ended his life in the arms of his son Vincenzo, of the Viviani, and of Evangelista Torricelli, who had been his disciple in the last months, on 8 January 1642. He was buried at Florence in S. Croce. - See plate CXXVII.
Bibliography11 works
On the third centenary of G.'s death, Essays and lectures, in the publications of the Catholic University, Milan 1942.