Galileo's Daughter (4 page)

“Imagine them joining together while falling,” he appealed to another debater. “Why should they double their speed as Aristotle claimed?" If the incongruity of these midair scenarios didn’t deflate Aristotle’s ideas, it was a simple enough matter to test his assertions with real props in a public setting.

Galileo never recorded the date or details of the actual demonstration himself but recounted the story in his old age to a young disciple, who included it in a posthumous biographical sketch. However dramatically Galileo may have executed the event, he did not succeed in swaying popular opinion down at the base of the Leaning Tower. The larger ball, being less susceptible to the effects of what Galileo recognized as air resistance, fell faster, to the great relief of the Pisan philosophy department. The fact that it fell only fractionally faster gave Galileo scant advantage.

“Aristotle says that a hundred-pound ball falling from a height of a hundred
braccia
[arm lengths] hits the ground before a one-pound ball has fallen one
braccio.
I say they arrive at the same time,” Galileo resummarized the dispute in its aftermath. “You find, on making the test, that the larger ball beats the smaller one by two inches. Now, behind those two inches you want to hide Aristotle’s ninety-nine
braccia
and, speaking only of my tiny error, remain silent about his enormous mistake.”

Indeed this was the case. Many philosophers of the sixteenth century, unaccustomed to experimental proof, much preferred the wisdom of Aristotle to the antics of Galileo, which made him an unpopular figure at Pisa.

When Vincenzio died in 1591 at the age of seventy, Galileo assumed financial responsibility for the whole family on a math professor’s meager salary of sixty
scudi
annually. (Professors in the more venerated field of philosophy made six to eight times as much, while a father confessor could earn close to two hundred
scudi
per year, a well-trained physician about three hundred, and the commanders of the Tuscan armed forces between one thousand and twenty-five hundred.) Galileo paid out dowry installments to his newly married sister Virginia’s fractious husband, Benedetto Landucci, supported his mother and sixteen-year-old brother, Michelangelo, and maintained his sister Livia at the Convent of San Giuliano until he could arrange for her to be wed. By this time, his three other siblings had all died of childhood diseases.

Galileo lent his help ungrudgingly, even enthusiastically. “The present I am going to make Virginia consists of a set of silken bed-hangings,” he had written home from Pisa just before her wedding. “I bought the silk at Lucca, and had it woven, so that, though the fabric is of a wide width, it will cost me only about three
carlini
[about one-hundredth of a
scudo
] the yard. It is a striped material, and I think you will be much pleased with it. I have ordered silk fringes to match, and could very easily get the bedstead made, too. But do not say a word to anyone, that it may come to her quite unexpectedly. I will bring it when I come home for the Carnival holidays, and, as I said before, if you like I will bring her worked velvet and damask, stuff enough to make four or five handsome dresses.”

In 1592, the year after he buried his father in the Florentine church called Santa Croce, Galileo left Pisa for the chair of mathematics at the University of Padua. If he had to forsake his native Tuscany for the Serene Republic of Venice, at least he enjoyed a more distinguished position there and increased his income to 180 Venetian florins per year.

The University of Padua, where Galileo taught for eighteen years

From the perspective of old age, Galileo would describe his time in Padua as the happiest period of his life. He made important friends with some of the republic’s great cultural and intellectual leaders, who invited him to their homes as well as to consult on shipbuilding at the Venetian Arsenale. The Venetian senate granted him a patent on an irrigation device he invented. Galileo’s influential supporters and quick-spreading reputation as an electrifying lecturer earned him raises that pushed his university salary to 300 and then to 480 florins annually. At Padua he also pursued the seminal studies of the properties of motion that he had begun in Pisa, for wise men regarded motion as the basis of all natural philosophy.

Fatefully during his Paduan idyll, while visiting friends outside the city, Galileo and two gentleman companions escaped the midday heat one afternoon by taking a siesta in an underground room. Natural air-conditioning cooled this chamber by means of a conduit that delivered wind from a waterfall inside a nearby mountain cave. Such ingenious systems ventilated numerous sixteenth-century villas in the Italian countryside but may have admitted some noxious vapors along with the welcome zephyrs, as apparently occurred in Galileo’s case. When the men awoke from their two-hour nap, they complained of various symptoms including cramps and chills, intense headache, hearing loss, and muscle lethargy. Within days, the strange malaise proved fatal for one of its victims; the second man lived longer but also died of the same exposure. Galileo alone recovered. For the rest of his life, however, bouts of pain, later described by his son as arthritic or rheumatic seizures, would strike him down and confine him to his bed for weeks on end.

Under happier circumstances—although no one knows precisely when or how—Galileo in Padua met Marina Gamba, the woman who shared his private hours for twelve years and bore him three children.

Marina did not share his house, however. Galileo dwelled on Padua’s Borgo dei Vignali (renamed, in recent times, Via Galileo Galilei). Like most professors, he rented out rooms to private students, many of them young noblemen from abroad, who paid to board under his roof for the duration of their private lessons with him. Marina lived in Venice, where Galileo traveled by ferry on the weekends to enjoy himself. When she became pregnant, he moved her to Padua, to a small house on the Ponte Corvo, only a five-minute walk away from his own (if one could have counted minutes in those days). Even after the ties between Marina and Galileo were strengthened by the growth of their family, their separate living arrangement remained the same.

Suor Maria Celeste Galilei, nee “Virginia, daughter of Marina from Venice,” was “born of fornication,” that is to say, out of wedlock, according to the parish registry of San Lorenzo in the city of Padua, on the thirteenth of August 1600, and baptized on the twenty-first. Marina was twenty-two on this occasion, and Galileo (though no mention divulges his identity), thirty-six. Such age discrepancies occurred commonly among couples at that time. Galileo’s own father had reached forty-two years before taking the twenty-four-year-old Giulia as his bride.

Engraving of Galileo at age thirty-eight, by Joseph Calendi

The following year, 1601, again in August, a registry entry on the twenty-seventh marked the baptism of “Livia Antonia, daughter of Marina Gamba and of—” followed by a blank space.

After five more years, on August 22, 1606, a third child was baptized, “Vincenzio Andrea, son of Madonna Marina, daughter of Andrea Gamba, and an unknown father.” Technically an “unknown father” for being unmarried to the mother, Galileo nevertheless asserted his paternity by giving the baby both grandfathers’ names.

Galileo recognized his illegitimate children as the heirs of his lineage, and their mother as his mate, although he ever avoided marrying Marina. Scholars by tradition tended to remain single, and the notations in the parish registry hint at circumstances that would have strengthened Galileo’s resolve. After all, she was “Marina from Venice"—not from Pisa or Florence, or Prato or Pistoia, or any other town within the bounds of Tuscany, where Galileo determined to return someday. And her heritage, “daughter of Andrea Gamba,” did not put her on a par with the poor but patrician Galilei family, whose ancestors had signed their names in the record books of a great city government.

[III]

Bright stars

speak of

your virtues

As his paduan career increased its brilliance in the early years of the seventeenth century, Galileo continued struggling to meet all his expensive family responsibilities. In 1600 his younger brother, the musical Michelangelo, was invited to play at the court of a Polish prince, and despite the maturity of his twenty-five years, he tapped Galileo for the clothing and money he needed to make the trip. Also in 1600, the same year Galileo saw the birth of his daughter Virginia, he found a husband for his sister Livia. Upon her marriage to Taddeo Galletti in 1601, Galileo negotiated the dowry, paid for the ceremony and the wedding feast, and also bought Livia’s dress, which was made of black Naples velvet with light blue damask that cost more than one hundred
scudi.
Then, in 1608, Michelangelo got married, moved to Germany, and reneged on his promised share of the sisters’ dowry contracts, precipitating a legal action by brother-in-law Benedetto Landucci, who complained of being cheated out of his expected sum.

Fortunately, Galileo’s endeavors led him to a new source of supplemental income. In the course of teaching military architecture and fortification to private students, he had invented his first commercial scientific instrument in 1597, called the geometric and military compass. It looked like a pair of metal rulers joined by a pivot, covered all over by numbers and scales, with screws and an attachable arch to hold the compass arms open at almost any angle. By 1599, after various modifications, the device functioned as an early pocket calculator that could compute compound interest or monetary exchange rates, extract square roots for arranging armies on the battlefield, and determine the proper charge for any size cannon. Shipwrights at the nearby Venetian Arsenale also adopted Galileo’s revolutionary compass, to help them execute and test new hull designs in scale models before building them full-size.

Galileo crafted the first few compasses himself but soon required the services of a full-time, live-in instrument maker to meet the popular demand. The hired craftsman moved into Galileo’s house with wife and children in tow, to work in exchange for salary, room and board for his whole family, all production materials, and a two-thirds share of the price of finished brass instruments, which sold for five
scudi
each. Galileo would not have made much money under these conditions, except that he charged every visiting student nearly twenty
scudi
to learn how to use the compass, and all of this was his to keep. At first he gave out a personally handwritten instruction manual as a learning aid; then in 1603 he hired an amanuensis to help generate enough copies— until three years later, when he hit on the idea of publishing the booklet for sale with the instrument.

He called his treatise
Operations of the Geometric and Military
Compass of Galileo Galilei, Florentine Patrician and Teacher of Mathematics in the University of Padua.
Its 1606 title page notes that the book was printed “in the Author’s House” and cannily dedicated to the future grand duke of Tuscany, Don Cosimo de’ Medici.