Galileo's Daughter

by Dava Sobel

  Father Grassi furthermore committed several mathematical mistakes in his calculations that led him to estimate the volume of the comet, body and “beard” together, at billions of times the size of the Moon—a ridiculous exaggeration in Galileo’s view. Worse, in describing his telescope observations of the comet, Father Grassi exposed his ignorance of the instrument’s fundamental principles, inviting Galileo’s scorn.

  Tycho Brahe’s system of the world

  Just at this juncture, Galileo’s student Mario Guiducci got elected consul of the prestigious Florentine Academy, which honor obliged him to present a pair of lectures in the spring of 1619. He chose comets as his topic. Galileo wrote much of the content for him, expressing his own bewilderment while negating the work of Tycho and Father Grassi: “Hence we must be content with what little we may conjecture here among shadows, until there shall be given to us the true constitution of the parts of the universe, inasmuch as that which Tycho promised us still remains imperfect.”

  Father Grassi took umbrage at the published version of these talks, which appeared in June 1619 under the title Discourse on the Comets. Galileo—for everyone rightly assumed him its author— seemed to have singled out the Jesuits as targets of attack: First Father Scheiner (the “Apelles” of the Sunspot Letters) and now Father Grassi—even though the Jesuit Collegio Romano had always upheld Galileo’s discoveries and treated him with great respect.

  Father Grassi’s angry, offended published rebuttal followed swiftly in the book Libra Astronomica, or Astronomical and Philosophical Balance, which he wrote in Latin under the pen name Lothario Sarsi, a purported student of his. As its title promised, the Libra of 1619 hung Galileo’s ideas about comets on a steelyard balance scale and found them weightless.

  Compelled to respond and silence the noisy barking of his opponents, Galileo began retorting right on the title page of his riposte. He called it II Saggiatore, or The Assayer—thus replacing the crude scale of the Libra with the more delicate balance assayers used to analyze the quantity of pure gold in gold ore. Father Grassi, retaliating again later in his turn, accidentally on purpose referred to this book as Assaggiatore, or Winetaster—to imply that Galileo, a notorious lover of good wine, had been drinking when he wrote The Assayer.

  In 1620, as the tenor of the comet debate turned nastier, the Holy Congregation of the Index raised the specter of the Edict of 1616 by announcing at last the necessary corrections that must be made to Copernicus’s text, De revolutionibus, in order to have it removed from the Index of Prohibited Books. The congregation insisted on watering down some dozen statements by Copernicus affirming the Earth’s motion, in order to make them sound more like hypothetical suggestions. Galileo dutifully penned the required changes into his own copy of Der revolutionibus, though he took care to cross out the offending passages with very light strokes.

  Galileo ventured no mention of the Copernican theory in The Assayer. Such discussion would have been imprudent, given the edict, but also irrelevant: Copernicus had not discussed comets in his book, and Galileo’s view of comets as optical illusions automatically divorced them from the order of the Sun and planets as far as he was concerned. He even derided “Sarsi” and “his teacher” for granting comets the status of quasi planets. “If their opinions and their voices have the power to call into existence the things they have considered and named,” quipped Galileo, “why then I beg them to do me the favor of considering and naming ‘gold’ a lot of old hardware that I have about my house.”

  Indeed, Galileo persisted, the play of the Sun’s light could set the most mundane objects aglitter, to fool the unsuspecting: “Sarsi has but to spit upon the ground and undoubtedly he will see the appearance of a natural star when he looks at his spittle from the point toward which the Sun’s rays are reflected.”

  Galileo took the occasion of The Assayer to mock the philosophical terms that masqueraded as scientific explanations in his day. He noted that sympathy, antipathy, occult properties, influences, and their like were all too often “employed by some philosophers as a cloak for the correct reply, which would be: ‘I do not know.’

  “That reply,” he reiterated, “is as much more tolerable than the others as candid honesty is more beautiful than deceitful duplicity.”

  Avoiding the forbidden topic of the world system, The Assayer thus considered the current comet controversy in the larger context of the philosophy of science. Galileo drew an unforgettable distinction between the experimental method, which he favored, and the prevailing dependence on received wisdom or majority opinion. “I cannot but be astonished,” Galileo wrote,

  that Sarsi should persist in trying to prove by means of witnesses something that I may see for myself at any time by means of experiment. Witnesses are examined in doubtful matters which are past and transient, not in those which are actual and present. A judge must seek by means of witnesses to determine whether Pietro injured Giovanni last night, but not whether Giovanni was injured, since the judge can see that for himself. But even in conclusions which can be known only by reasoning, I say that the testimony of many has little more value than that of few, since the number of people who reason well in complicated matters is much smaller than that of those who reason badly. If reasoning were like hauling I should agree that several reasoners would be worth more than one, just as several horses can haul more sacks of grain than one can. But reasoning is like racing and not like hauling, and a single Barbary steed can outrun a hundred dray horses.

  It took Galileo two years to complete The Assayer, beset as he was throughout by many family and official matters. Marina Gamba died in February 1619, leaving Galileo’s children officially motherless. Having helped both his daughters take the veil, Galileo now atoned for the messy circumstances of his son’s birth by getting Grand Duke Cosimo II to legitimize Vincenzio on June 25, two months before the boy’s thirteenth birthday. Cosimo handled this matter-of-factly enough, knowing his own Medici forebears to have fathered at least eight illustrious illegitimate sons, two of whom had become cardinals—and one of those had traded the cardinal’s biretta for the pope’s tiara as His Holiness Clement VII.

  Meanwhile Galileo’s mother, Madonna Giulia, grew older and ever crankier at the house in Florence where she had stayed when her son moved to Bellosguardo. “I hear with no great surprise that our mother is being so dreadful,” Galileo’s brother, Michelangelo, commiserated in October 1619 from the safe distance of Munich. “But she is much aged, and soon there will be an end to all this quarreling.”

  Madonna Giulia died in September 1620, at eighty-two. Her death was soon followed by the publicly mourned passing of the grand duke, only thirty years of age, in February 1621. Cosimo II, who had come to power at nineteen, now bequeathed the Grand Duchy of Tuscany to the eldest of his eight children, ten-year-old Ferdinando II. The boy also inherited Cosimo’s chief mathematician and court philosopher, for Galileo’s appointment carried a lifetime tenure. Until Ferdinando reached majority, however, he deferred perforce in all matters to the judgment of his regents: his mother, Archduchess Maria Maddalena of Austria, and his grandmother, the dowager Grand Duchess Cristina of Lorraine.

  The necrology of the year 1621 also listed two major figures behind the anti-Copernican edict: Roberto Cardinal Bellarmino, later to be canonized Saint Robert Bellarmine, and Pope Paul V, the founder of the Vatican Secret Archives, where certain papers pertaining to Galileo’s 1616 trip to Rome already resided among centuries’ worth of private papal documents. Paul V, who had promised to protect Galileo for the rest of his life, died of a stroke January 28. A little over a week later, on February 9, the Sacred College of Cardinals suddenly and unanimously acclaimed his successor, Alessandro Ludovisi of Bologna, as Pope Gregory XV. But the new pontiff’s frail health, of which the cardinals had been well aware at the time of his selection, would end his papacy in less than two years.

  Galileo fell ill again in early 1621. He recovered by midyear and completed most of The Assayer by year’s end
. He composed the long polemic in the form of a letter to his friend and fellow Lyncean in Rome, Virginio Cesarini, Prince Cesi’s young cousin, who had been smitten by science under Galileo’s influence and written to him during the comet season to offer details of his own cometary observations.

  “I have never understood, Your Excellency,” Galileo addressed Cesarini plaintively in the opening pages of The Assayer, “why it is that every one of the studies I have published in order to please or to serve other people has aroused in some men a certain perverse urge to detract, steal, or deprecate that modicum of merit which I thought I had earned, if not for my work, at least for its intention.”

  In October 1622, Galileo delivered the long-awaited polished manuscript to Cesarini, who fine-tuned it further in collaboration with Prince Cesi before publication. As the printing neared completion the following summer, however, a puff of white smoke from the Sistine Chapel called the process to a halt.

  Pope Gregory was dead. Galileo’s longtime acquaintance and admirer, Maffeo Cardinal Barberini, now succeeded him as Pope Urban VIII.

  Quickly, Prince Cesi created a new engraved title page incorporating the three bees of the Barberini coat of arms. Though Galileo had addressed The Assayer to Virginio Cesarini, the Lynceans seized the political expedient of dedicating the book to the new pontiff. They offered up The Assayer, which had grown out of a spiteful argument over a trio of comets, as their literary entree into the papal court of Urban VIII.

  PART TWO

  On

  Bellosguardo

  [IX]

  How our

  father is

  favored

  MOST ILLUSTRIOUS LORD FATHER

  The happiness I derived from the gift of the letters you sent me, Sire, written to you by that most distinguished Cardinal, now elevated to the exalted position of Supreme Pontiff, was ineffable, for his letters so clearly express the affection this great man has for you, and also show how highly he values your abilities. I have read and reread them, savoring them in private, and I return them to you, as you insist, without having shown them to anyone else except Suor Arcangela, who has joined me in drawing the utmost joy from seeing how much our father is favored by persons of such caliber. May it please the Lord to grant you the robust health you will need to fulfill your desire to visit His Holiness, so that you can be even more greatly esteemed by him; and, seeing how many promises he makes you in his letters, we can entertain the hope that the Pope will readily grant you some sort of assistance for our brother.

  In the meantime, we shall not fail to pray the Lord, from whom all grace descends, to bless you by letting you achieve all that you desire, so long as that be for the best.

  I can only imagine, Sire, what a magnificent letter you must have written to His Holiness, to congratulate him on the occasion of his reaching this exalted rank, and, because I am more than a little bit curious, I yearn to see a copy of that letter, if it would please you to show it, and I thank you so much for the ones you have already sent, as well as for the melons which we enjoyed most gratefully. I have dashed off this note in considerable haste, so I beg your pardon if I have for that reason been sloppy or spoken amiss. I send you loving greetings along with the others here who always ask to be remembered to you.

  FROM SAN MATTEO, THE 10TH DAY OF AUGUST.

  Most affectionate daughter,

  S.M.C.

  Only four days previously, on August 6,1623, Maffeo Cardinal Barberini stood sweating in the Sistine Chapel, where he and more than fifty fellow cardinals had been locked together since mid-July in papal election proceedings. Absent the unified conviction, inspired by the Holy Spirit, that had led to the acclamatio selection of Gregory XV two years before, the Sacred College of Cardinals now prayed for guidance in the balloting. The members voted twice a day, morning and afternoon, each one prohibited from endorsing himself, and all of them disguising their handwriting to maintain the secrecy of the selection process. Every time the tabulation failed to produce the required two-thirds majority, the cardinal scrutineers bound the slips of paper and burned them in a special stove with wet straw, which sent up the black smoke of indecision. The typical heat and malaria that visited Rome every summer claimed the lives of six elderly cardinals in the conclave before the assembly at last cast fifty of its fifty-five ballots for Barberini as the new leader of the Church.

  Florence in the late sixteenth century

  “Do you, Most Reverend Lord Cardinal,” the chamberlain asked him face to face, “accept your election as Supreme Pontiff, which has been canonically carried out?”

  “Accepto,” he answered with the only word required.

  “By what name will you be known?” The choices included his own Christian name, Maffeo, or the name of any pope who had preceded him—except Peter, of course, which tradition forbade.

  At a stroke, Maffeo Barberini metamorphosed into Pope Urban VIII. The ballots, burned with dry straw instead of wet this time, announced their white smoke signal to the crowds around the Vatican, and soon the declaration “We have a pope!” justified the crescendoing ecstasy of their cries.

  Galileo, recognizing the potential personal boon of this turn of events, shared his excitement with Suor Maria Celeste by sending her a sheaf of letters that spanned a decade of pleasant exchanges. These dated from Cardinal Barberini’s first letter to Galileo in 1611, when he called him a virtuous and pious man of great value whose longevity could only improve the lives of others. The passing years had fanned the cardinal’s ardor, so that his 1620 poem, “Dangerous Adulation,” not only cited Galileo as the discoverer of wondrous new celestial phenomena but also used his sunspots as a metaphor for dark fears in the hearts of the mighty. In closing the cover letter to Galileo that accompanied this poetic tribute, the cardinal had signed himself—with noteworthy warmth—“as your brother.”

  Galileo naturally took a more deferential tone in his responses, noting sentiments such as, “I am your humble servant, reverently kissing your hem and praying God that the greatest felicity shall be yours.” He wrote as often as necessary to keep Cardinal Barberini updated on his scientific work and sent him a copy of each of his books, as well as his unpublished “Treatise on the Tides,” and Guiduccfs Discourse on the Comets.

  The most recent letter from the cardinal bore the date June 24, 1623, just weeks prior to his accession, in which he thanked Galileo for guiding a favorite nephew, Francesco Barberini, through the successful completion of doctoral studies at Pisa.

  Galileo wanted nothing so much as to travel to Rome in August to kiss the feet of the new pope and march with his fellow Lyncean Academicians in Urban’s investiture procession. The exciting early days of the Barberini pontificate overflowed with promise for all artists and scientists, and particularly those from Urban’s native Florence. Striking now, Galileo thought he might well secure the pope’s blessing for his own most sensitive projects, and at the same time ensure his son’s future.

  VRBANVS VIII. BARBERINVS PONT. MAX.

  Urban VIII in the first year of his pontificate

  Galileo had sent Vincenzio off to law school at the University of Pisa the previous year. Now he hoped to obtain a pension for him—a title as a canon that would guarantee Vincenzio a small annual base income for the rest of his life in exchange for little or no real work. Such sinecures influenced the economy of seventeenth-century Italy, often draining the revenues of small dioceses while filling the pockets of absentee landlords, at least half of whom were laymen. Despite the abuses of this system, however, Rome not only tolerated it but also supervised it, because the pensions supported so many more prelates than the papal treasury could afford to pay.

  As for Suor Maria Celeste’s request to see a copy of her father’s congratulatory letter to Urban, Galileo denied it on the grounds that he had not written one. He explained to her that although he enjoyed a most cordial relationship of long standing with His Holiness—enabling him to dedicate his new book to the pope and confidently anticipate a p
rivate audience at the Vatican—protocol argued against a personal note on this occasion. Instead, he had proffered his congratulations through the proper channel of Urban’s nephew Francesco, who had been Galileo’s student.

  “It was through your most gentle and loving letter,” Suor Maria Celeste confessed a few days later, “that I became fully aware of my backwardness, in assuming as I did that you, Sire, would perforce write right away to such a person, or, to put it better, to the loftiest lord in all the world. Therefore I thank you for pointing out my error, and at the same time I feel certain that you will, by the love you bear me, excuse my gross ignorance and as many other flaws as find expression in my character. I readily concede that you are the one to correct and advise me in all matters, just as I desire you to do and would so appreciate your doing, for I realize how little knowledge and ability I can justly call my own.”

  The date of this letter, August 13, marked Suor Maria Celeste’s twenty-third birthday, although she made no reference to that fact. She reckoned the accumulation of her years now by the anniversary of her nun’s vows on October 4, and by the feast day of the Holy Virgin Mary, whose name she had taken, on September 8.

  Within a week she learned that illness had scotched Galileo’s travel plans and forced him into Florence to the home of his late sister, where his recently widowed brother-in-law and his nephew were taking care of him. The news arrived via the steward of San Matteo, a hired man who lived on the convent grounds with his wife, helping the nuns by tending to the heavy work and the traffic with the outside world.