Читать книгу Galileo’s Daughter: A Drama of Science, Faith and Love - Дава Собел - Страница 13

GALILEO’S COLLECTED CORRESPONDENCE brims with allusions to illnesses that often kept him from replying sooner to someone or forced him to close a letter in haste. Changes in the weather ‘molested’ him, his first biographer noted, and he typically fell sick in spring or autumn, or both, about every other year throughout his adult life. Although Galileo rarely elaborated on the nature of these health crises, he may have suffered from some form of relapsing fever contracted during the cave incident in Padua. Or he may have been a victim of malaria or typhoid, a common enough plight in Italy during that period. Another possible explanation for his pattern of repetitive malaise is an unspecified rheumatic disease, possibly gout, which could have accounted for the ‘very severe pains and twinges’ his biographer said he sustained ‘in various parts of his body’. Gout also causes painful kidney stones (when the excess uric acid in the blood, typical of this disease, gets deposited as crystals in the kidneys as well as in the joint spaces), and Galileo complained more than once of prolonged kidney trouble. The quantities of red wine he produced and drank would only have exacerbated the condition (by raising his uric acid level). Even at a time when wine was generally considered the safer alternative to water, doctors recognised the causal connection between alcohol and attacks of gout. Galileo’s daughter, who made many of his pills and tonics in the convent apothecary shop, frequently counselled him in her letters to limit ‘the drinking that is so hurtful to you’ because of the ‘great risk of getting sick’.

Other symptoms Galileo sometimes singled out for specific mention included chest pain, a hernia for which he wore a heavy iron truss, insomnia, and various problems with his eyes – particularly unfortunate for an astronomical observer. ‘As a result of a certain affliction I began to see a luminous halo more than two feet in diameter around the flame of a candle’, Galileo wrote of one such condition to a colleague, ‘capable of concealing from me all objects which lay behind it. As my malady diminished, so did the size and density of this halo, though more of it has remained with me than is seen by perfect eyes.’ His frequent telescope demonstrations may have predisposed him also to ocular infections, easily communicated by sharing an eyepiece.

After Galileo moved to Florence in 1610, poor health and long periods of recuperation frequently drove him out of the city into the surrounding hills. ‘I shall have to become an inhabitant of the mountains,’ Galileo vowed while he and his mother and the two little girls still resided on a city street, ‘otherwise I shall soon dwell among the graves.’

For several ensuing years he relied gratefully on the hospitality of his friend and follower Filippo Salviati, who rescued Galileo from the foul city air. At Salviati’s Villa delle Selve in the hills of Signa, fifteen miles west of Florence, Galileo spent enough time to write the better part of two books – Bodies in Water and Sunspot Letters – while convalescing from his typical ills. When his ready access to this retreat ended in 1614 with Salviati’s death, Galileo pressed the search for his own year-round haven.

In April of 1617, he took a fine villa atop the hill called Bellosguardo (‘beautiful sight’) on the south side of the River Arno, offsetting the high annual rent of one hundred scudi by selling the grain and broad beans grown on the property. From his new eyrie, Galileo enjoyed an unobstructed panorama of the heavens, with a downwards vista that swept the russet roofs, domed churches and city walls of Florence. To the east he could see the olive-green hillside of Arcetri, where his daughters lived inside the walled Convent of San Matteo. It took him three-quarters of an hour on foot or by mule – when he was up to the trip – to visit them.

Despite the salubrious atmosphere at Bellosguardo, however, another serious illness struck Galileo towards the end of 1617 and held him in its grip until spring came. In May 1618, thankful to be freed from his sickbed at last, he set out on a pilgrimage across the Apennine Mountains to the Adriatic coast, where he visited the ‘Casa Santa’ – the House of the Virgin Mary in Loreto. This former residence of the Blessed Virgin, according to local legend, had abruptly uprooted itself from the Holy Land in the year 1294 and flown on the wings of angels to the laurel grove (loreto in Italian) that gave the present town its name. Galileo had first talked of worshipping at the popular shrine in 1616, after he escaped unscathed from the Copernican uproar in Rome, but events and maladies had kept him from fulfilling that intention until now, when he could also offer thanks for his recent recovery and pray for improved health in the future.

He returned home in June to Bellosguardo and to his son, Vincenzio, whom he had brought from Padua in 1612 at the age of seven. By 1618, their male-dominated household also included two new students, Mario Guiducci and Niccolò Arrighetti, who, like Castelli before them and others to come after, would remain Galileo’s devoted friends for life. The thirtyish scholars busied themselves all that summer copying the master’s early theorems on motion, to help him return to the fundamental work he had forsaken in 1609 for the telescope. They mined the dense jumble of his Paduan notes and prepared neat sheets of paper, written extravagantly on one side only, for his review and revision.

In September, just when Galileo’s student assistants had finished this preliminary work, another bout of illness prevented him from building on it as planned. The delay might have been merely temporary, except that while Galileo languished, the heavens sent him a new mystery to ponder, and this apparition initiated a cascade of events that postponed the publication of his motion studies for another two decades.

A small comet glowed in the skies over Florence that September of 1618. Though unspectacular, as comets go, it was nevertheless the first comet to appear since the birth of the telescope. Other astronomers took to their rooftops with instruments of Galileo’s design, but Galileo himself remained indoors an invalid. Then another comet arrived in mid-November, while Galileo unfortunately fared no better than before. And even by the end of November, when a truly brilliant third comet burst on the scene to garner the attention of observers all over Europe, Galileo still could not stand among them.

‘During the entire time the comet was visible’, he reported later, ‘I was confined by illness to my bed. There I was often visited by friends. Discussions of the comets frequently occurred, during which I had occasion to voice some thoughts of mine which cast doubt upon the doctrines that have been previously held on this matter.’ In fact, Galileo saw only one important comet his whole life – the big bright one of 1577, in his youth – and never did figure out what these objects really were.

Most of Galileo’s contemporaries feared comets as evil omens. (Indeed the three 1618 examples were presently seen, with hindsight, as heralds of the Thirty Years’ War, which broke out in Bohemia the same year.) Aristotelian philosophers figured comets for atmospheric disturbances. The fact that comets came and went, changing their fuzzy-glow appearance all the while, automatically relegated them to the sublunar sphere between the Earth and the Moon, where they were thought to be ignited by friction of the spheres’ turning against the upper reaches of the air.

It may seem incredible that Galileo resisted the temptation to go outdoors in the autumn of 1618 long enough to view any one of the three comets, especially since he felt well enough to enter into intellectual discussions with visitors. But in fact the November night air held terrible danger for him, a man well past fifty now, who had spent most of the current year battling one malady after another. Moreover, as Galileo no doubt knew from his friends’ accounts, he would not have seen much even if he had risked his own study of these objects. A comet, or ‘hairy star’, retained its blurred contours despite the aid of the most powerful telescope.^* Unlike the fixed stars that resolved into points of light when the telescope stripped them of their rays, or planets that turned to tiny globes, a comet could not be brought into sharp focus. And Galileo held back because he believed – in agreement for once with his Aristotelian contemporaries, though not for the same reasons – that comets belonged to the Earth’s atmosphere.

Galileo thus rejected the findings of his Danish predecessor, Tycho Brahe, who had observed the great comet of 1577 and another in 1585. Tycho, probably the most able naked-eye stargazer who ever lived, followed that comet every night with his oversized measuring instruments to determine its position. It lay beyond the Moon, he discovered through position studies, perhaps as far as Venus, and that meant one of two things to his sixteenth-century way of thinking: either the comet had come crashing through Aristotle’s crystalline celestial spheres, or the celestial spheres did not exist. Tycho chose the latter scenario, emboldened by having been the first European, in 1572, to identify a nova, which convinced him that changes could occur in the ‘immutable’ heavens.

Galileo, when he witnessed the next nova in 1604, backed the deceased Tycho’s interpretation of the new star’s nature and significance. But he despised Tycho’s planetary system for its poor compromise between Ptolemy and Copernicus. And as for the comet Tycho had tracked so carefully, Galileo dismissed it as a will-o’-the-wisp. He took comets to be anomalous illuminations in the air – most likely reflections of sunlight bounced off high-altitude vapours – not heavenly bodies per se. You could no more gauge the distance to a comet, Galileo believed, than you could catch a rainbow or contain the aurora borealis.

None of the news, notes or queries on the 1618 comets that reached Galileo shook him from his sceptical stance. Nor was he impressed by the pamphlet sent him from Rome containing a comet lecture delivered at the Collegio Romano and published in early 1619. Its author, Jesuit astronomer Father Orazio Grassi, argued on the basis of his studies that the path of the late-November comet carried it between the Sun and the Moon. This was a remarkable conclusion for any Jesuit to reach, because the Collegio Romano did not dispute Aristotle lightly. Nevertheless, Galileo doubted Father Grassi’s distance estimates, just as he had questioned Tycho’s, on the grounds that comets had no substance. 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.

Just at this juncture, Galileo’s student Mario Guiducci was elected consul of the prestigious Florentine Academy, which honour 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 to be 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 analyse 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 spectre 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 De 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 favour 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 towards 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 favoured, and the prevailing dependence on received wisdom or majority opinion. ‘I cannot but be astonished 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,’ Galileo wrote.

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 legitimise Vincenzio on 25 June, 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 grouchier 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 quarrelling.’