Galileo's Daughter

by Dava Sobel

  At the Pisan academic ceremonies, Vincenzio collected his doctoral degree in law as the culmination of six years of study. (Galileo himself had never experienced this rite of passage, having left school without completing his required courses.) A more mature Vincenzio now returned home to his father’s house at Bellosguardo, where he turned twenty-two in August. He took to paying regular visits to his sisters at San Matteo. And the following December he delighted Galileo with his decision to marry young Sestilia Bocchineri, whose family held prestigious appointments in the Tuscan court.

  MOST BELOVED LORD FATHER

  THE UNEXPECTED NEWS delivered here by our Vincenzio regarding the finalization of his wedding plans, and marrying into that esteemed family, has brought me such happiness that I would not know how better to express it, save to say that, as great as is the love I bear you, Sire, equally great is the delight I derive from your every joy, which I imagine in this instance to be immense; and therefore I come now to rejoice with you, and pray our Lord to protect you for a very long time, so that you can savor those satisfactions that seem guaranteed to you by the good qualities of your son and my brother, for whom my affection grows stronger every day, as he appears to me to be a calm and wise young man.

  I would much rather have celebrated with you in person, Sire, but if you would be so kind, I implore you to at least tell me by letter how you plan to arrange your visit with Vincenzio’s betrothed: meaning whether it may be well to meet in Prato when Vincenzio goes there, or better to wait until she is in Florence, since this is the usual formality among us sisters, and surely, given her experience of having been in a convent, she will know these customs. I await your resolution. And in the meanwhile I bid you adieu from my heart.

  Your most affectionate daughter,

  S. M. Coloste

  [XV]

  On the

  right path,

  by the

  grace of God

  The family of Sestilia Bocchineri, Vincenzio’s intended, lived above reproach about twelve miles from Florence in the textile city of Prato, famed for its mulberry trees and silkworms. There her father served as majordomo at the Medici’s local palace, while her brother Geri held a Florentine court position at the Pitti. The Tuscan secretary of state had contrived to couple Vincenzio with Sestilia, entirely to Galileo’s satisfaction. The bride brought a dowry of seven hundred scudi to the marriage—an amount that would have secured her future in her convent had she not been betrothed instead on the eve of her sixteenth birthday. The wedding date, set for January 29, 1629, allowed the relatives about a month’s time for preparations.

  Although Suor Maria Celeste could not leave San Matteo to attend any of her brother’s nuptial festivities, she determined to cater at least part of the wedding feast, to spare her father yet another financial burden. “Here then is a list of the more costly items that we will need for making a platter of pastries,” she wrote him on January 4, enclosing a short shopping list of pricey staples— white sugar, almonds, and fine confectioners’ sugar—on a small separate square of paper, “leaving the less expensive ingredients to me. After this, Sire, you will be able to see if you want me to cook other sweet things for you, such as savories and the like; because I firmly believe you would spend less this way than buying them already prepared by the grocer’s shop, and we will apply ourselves to making them with the utmost possible care.”

  As for the bride’s gift, “My thoughts lean toward sewing her a beautiful apron,” Suor Maria Celeste said later in the same letter, “so as to give her something that would be useful, and not require a great expenditure on our part, since we could do all the work ourselves; not to mention that we have no idea how to fashion the high collars and ruffs that ladies are wearing nowadays.

  “I might think I had blundered, Sire,” she added, “asking your opinion on these many trifles, if I were not absolutely certain that you, in small details just as in great matters, know far more than we nuns do.”

  For his own gift, Galileo helped the newlyweds buy a putty-colored house with a garden and courtyard on the Costa San Giorgio, partway up the road that ascended from Florence to Arcetri.

  The month after the wedding, in the course of Galileo’s continuing correspondence with his faithful friend Castelli, the monk raised the old subject of the solar spots. And Galileo, who prided himself on having long since discovered and published everything worth saying about sunspots, presently began to see a new significance in their behavior that could confirm the Copernican world system. Within a few months, the sunspots would light Galileo’s way back to his long-neglected Dialogue.

  Castelli, age fifty, now lived in Rome, where Pope Urban VIII had summoned him as a specialist in hydraulics to supervise water and drainage projects around the Holy City. Urban had performed the same kind of consulting work himself years before, when he regulated the waters of Lake Trasimeno for Pope Clement VIII, so he recognized Castelli’s expertise. While in Rome, Castelli also taught physics at the college called the Sapienza, and wrote a book in 1628 about how to measure running water. He sent Galileo a copy for comment, and during this exchange, late in February 1629, Castelli mentioned the imminent publication of a major new text on sunspots by Galileo’s old rival, Father Christopher Scheiner—the “Apelles” of the Sunspot Letters. (Printing problems, however, delayed the appearance of Scheiner’s book, Rosa Ursina, for another two years, until April of 1631.)

  Father Christopher Scheiner

  Castelli also detailed recent observations of a gigantic sunspot that called attention to itself over a period of several weeks. The spot had crossed the body of the Sun, disappearing at length around its western limb on February 9, only to reappear a fortnight later—still recognizable—on February 24, on the Sun’s eastern horizon.

  The thought of Scheiner’s reprise of sunspots must have nettled Galileo, for he denounced the forthcoming book in his April correspondence, predicting an assortment of errors and irrelevancies. In private, however, he perused his old sunspot files to see what, if anything, he might have missed before. And indeed he had missed something: He had overlooked the odd way the spots traversed the Sun over the course of the year. Their path appeared occasionally to cut straight across the Sun’s middle, and at other times to trace an upward or a downward slanting arc. Galileo surmised, toward the summer of 1629, that the spots probably stayed a steady course around the Sun’s equator all the time. They merely appeared to trek uphill or down as the seasons changed because of the annual revolution of the tilted Earth around the also-tilted Sun.

  The Sun thus offered its own physical evidence in support of Copernicus, compounding the testimony of the tides.

  What a blow to think that Scheiner, who had foolishly mistaken sunspots for stars before Galileo corrected him, now stood ready to publish this monumental discovery! The shock impelled Galileo back to his unfinished manuscript. If he needed further incentive, he could look to the projected income from sales of the finished book, for his new daughter-in-law was already pregnant, his son still unemployed, and Suor Maria Celeste anxious to improve the quality of her life through the purchase of private quarters in the convent.

  MOST BELOVED LORD FATHER

  THE DISCOMFORT I HAVE ENDURED ever since I came to live in this house, for want of a cell of my own, I know that you know, Sire, at least in part, and now I shall more clearly explain it to you, telling you that two or three years ago I was compelled by necessity to leave the one small cell we had, for which we paid our novice mistress (according to the custom we nuns observe) thirty-six scudi, and give it over totally to Suor Arcangela, so that (as much as possible) she could distance herself from this same mistress, who, tormented to distraction by her habitual moods, posed a threat, I feared, to Suor Arcangela, who often finds interaction with others unbearable; beyond that, Suor Arcangela’s nature being very different from mine and rather eccentric, it pays for me to acquiesce to her in many things, in order to be able to live in the kind of peace and unity befitting
the intense love we bear each other. As a result I spend every night in the disturbing company of the mistress (although I get through the nights easily enough with the help of the Lord, who suffers me to undergo these tribulations undoubtedly for my own good) and I pass the days practically a pilgrim, having no place whatsoever where I can retreat for one hour on my own. I do not yearn for large or very beautiful quarters, but only for a little bit of space, exactly like the tiny room that has just become available, now that a nun who desperately needs money wants to sell it; and, thanks to Suor Luisa’s having spoken well on my behalf, this nun prefers me over any of the others offering to buy it. But because its price is 35 scudi, while I have only ten, which Suor Luisa kindly gave me, plus the five I expect from my income, I cannot take possession of the room, and I rather fear I may lose it, Sire, if you do not assist me with the remaining amount, which is 20 scudi.

  I explain this need to you, Sire, with a daughter’s security and without ceremony, so as not to offend that loving tenderness I have experienced so often. I will only repeat that this is of the greatest necessity, on account of my having been reduced to the state in which I find myself, and because, loving me the way that I know you love me, and desiring my happiness, you can well imagine how this step will bring me the greatest satisfaction and pleasure, of a proper and honest sort, as all I seek is a little quiet and solitude. You might tell me, Sire, that to make up the sum I require, I could avail myself of the 30 scudi of yours that the convent is still holding: to which I respond (aside from the fact that I could not lay claim to that money quickly enough in this extreme case, as the nun selling the room faces dire straits) that you promised the Mother Abbess you would not ask her for those funds until such time as the convent enjoyed some relief from the constraint of constant expenditures; given all that, I do not think you will forsake me, Sire, in doing me this great charitable service, which I beg of you for the love of God, numbering myself now among the neediest paupers locked in prison, and not only needy, I say, but also ashamed, since I would not dare to speak so openly of my distress to your face: no less to Vincenzio; but only by resorting to this letter, Sire, can I appeal with every confidence, knowing that you will want and be able to help me. And here to close I send you regards with all my love, and also to Vincenzio and his bride. May the Lord bless you and keep you happy always.

  FROM SAN MATTEO, THE 8TH DAY OF JULY 1629.

  Most affectionate daughter,

  S.M.Coloste

  The novice mistress, from whom Suor Maria Celeste and Suor Arcangela purchased their first small room for thirty-six scudi, had been chosen by the abbess as the one to “form them in holy living and becoming behavior,” according to the practice of the order. But the mistress, who is never mentioned by name in any of Suor Maria Celeste’s letters, herself abused the Rule because of serious emotional disturbances that provoked her to constant prattling.

  The Sisters must keep silence from the hour of Compline until Terce. . . . Let them also be silent continually in the church, in the dormitory, [RULE OF SAINT CLARE, chapter V]

  Most of the residents of San Matteo slept in a common dormitory, though the convent contained numerous private chambers that could be bought for a price—over and above the dowry a nun’s family members paid to the monastery, and in addition to the allowance they meted out to her for living expenses. In this sense, although every Poor Clare lived in poverty, some lived more poorly than others. And yet, because the sisters dined together and shared the same food, the convent’s income from the sale of private quarters served to improve the fare for all.

  It may not be allowed any Sister to send out letters, or to receive anything, or to give anything outside the monastery without permission of the Abbess. Nor is it allowed to have anything which the Abbess has not given or permitted. But if anything should be sent to a Sister by her relatives or by others, the Abbess should have it given to the Sister. Then, if she needs it, she may use it; otherwise, let her charitably give it over to a Sister in need. If, however, any money would be sent to a Sister, the Abbess with the advice of the Discreets should have provision made for her in those things she may need, [RULE OF SAINT CLARE, chapter VIII]

  Galileo sent Suor Maria Celeste the twenty scudi, naturally, but her living situation held even more complexity and danger than the self-conscious, convoluted language of her request could indicate. In fact she required several months to resolve her plight and find the courage to explain the full chain of events involving the money, the mistress, and the cell to her father, who had resumed his ruminations on the two chief systems of the world.

  “And to give you some news of my studies,” he wrote on October 29 to his lawyer friend Elia Diodati in Paris, ‘you must know that a month ago I took up again my Dialogue about the tides, put aside for three years on end, and by the grace of God have got on the right path, so that if I can keep on this winter I hope to bring the work to an end and immediately publish it.” The two men had met when Diodati visited Florence in 1620 and had maintained an intellectual correspondence ever since. To Diodati, who had been born in Italy but moved first to Geneva and then to Paris because of his family’s Protestant faith, Galileo could be perfectly blunt about his book’s pro-Copernican slant. “In this, besides the material on the tides, there will be inserted many other problems and a most ample confirmation of the Copernican system by showing the nullity of all that had been brought by Tycho and others to the contrary. The work will be quite large and full of many novelties, which by reason of the freedom of dialogue I shall have scope to introduce without drudgery or affectation.”

  Diagram from Day Three of Galileo’s Dialogue

  demonstrating the Copernican system

  He presented the new sunspot evidence on Day Three of the Dialogue, the day devoted to the discussion of the Earth’s annual motion. It came up right after a spirited demonstration of the planetary positions, in which Salviati showed how the errant wanderings of Mercury, Venus, Mars, Jupiter, and Saturn could all be explained by the Earth’s plying a yearly orbit, between the orbits of Venus and Mars, around the Sun.

  “But another effect,” Salviati adds without pausing for breath, “no less wonderful than this, and containing a knot perhaps even more difficult to untie, forces the human intellect to admit this annual rotation and to grant it to our terrestrial globe. This is a new and unprecedented theory touching the Sun itself. For the Sun has shown itself unwilling to stand alone in evading the confirmation of so important a conclusion, and instead wants to be the greatest witness of all to this, beyond exception. So now hear this new and mighty marvel.”

  And he proceeds to describe how the sunspots alter their apparent path, from the straight line that could be observed only two days out of every 365 (at the summer and winter solstices), to an arc that curves upward for half the year and downward for the other six months. Anyone who clung to the Ptolemaic system— who insisted the Sun spun around the Earth every day—now had to explain why the sunspots changed the angle of their path according to an annual cycle, and not a daily one. Some Aristotelian stalwarts might dredge up the old dismissal of the sunspots as vain illusions of the telescope lenses. More serious and scientific followers of Ptolemy, however, would have to spiral the Sun through the most complex gyrations imaginable, in order to save these newly recognized appearances in a geocentric and geostationary system.

  Salviati’s explication of the sunspot connection fills only ten pages of dialogue, including a couple of diagrams to help Sagredo and Simplicio grasp the concept. The three discussants thus find ample time on the third day to consider other imponderables—the size and shape of the firmament, for example—and to converse in awe about the confounding grandeur of space.

  Responding to Simplicio’s Aristotelian vision of the Earth as the center of the world, the center of the universe, the hub of the stellar sphere, Salviati proposes something vaster and vaguer: “I might very reasonably dispute whether there is in Nature such a center, seeing that neith
er you nor anyone else has so far proved whether the universe is finite and has a shape, or whether it is infinite and unbounded.”

  This very modern idea of a universe without end had occurred to Copernicus but also helped kindle the fire that executed Giordano Bruno, as Galileo knew. He dropped the subject quickly yet returned again and again in the Dialogue to the evident enormity of the heavens.

  Copernicus had pushed the stars away to unimaginable distances to explain their constancy in contrast to the planets. The reason the stars never seemed to rock this way or that as the Earth traveled all around the Sun over the course of the year, Copernicus explained, was that they lay too far away for any shift in position, or parallax, to be perceived. Galileo agreed, and furthermore predicted that improved observations through powerful future instruments would one day reveal this annual stellar parallax.*

  Simplicio and his fellow Aristotelian philosophers really hated the big, unwieldy universe of Copernicus. They could not believe that God would have wasted so much space on something of no possible use to man.

  “It seems to me that we take too much upon ourselves, Simplicio,” counters Salviati, “when we will have it that merely taking care of us is the adequate work of Divine wisdom and power, and the limit beyond which it creates and disposes of nothing. I should not like to have us tie its hand so. . . . When I am told that an immense space interposed between the planetary orbits and the starry sphere would be useless and vain, being idle and devoid of stars, and that any immensity going beyond our comprehension would be superfluous for holding the fixed stars, I say that it is brash for our feebleness to attempt to judge the reason for God’s actions, and to call everything in the universe vain and superfluous which does not serve us.”