Galileo’s Daughter: A Drama of Science, Faith and Love. Dava Sobel

day. The ‘wandering’ stars, or planets – Mercury, Venus, Mars, Jupiter and Saturn – moved against the background of the fixed stars in a complex pattern. Galileo became the first to distinguish them further: ‘Planets show their globes perfectly round and definitely bounded, looking like little moons, spherical and flooded with light all over; fixed stars are never to be seen bounded by a circular periphery, but have rather the aspect of blazes whose rays vibrate about them, and they scintillate a very great deal.’^*

      He pursued this new nocturnal fascination through the winter, plagued by the cold and the difficulty of keeping the instrument steady against the trembling of his hands and the beating of his heart. He needed to wipe the lenses repeatedly with a cloth, ‘or else they become fogged by the breath, humid or foggy air, or by the vapour itself which evaporates from the eye, especially when it is warm’. Early in January, he fell on the most extraordinary discovery of all: ‘four planets never seen from the beginning of the world right up to our day’, in orbit around the planet Jupiter.

      Beyond their enormous astronomical significance, the new Jovian planets held special meaning for a friend of the Florentine court. Cosimo I of glorious memory had created a classical mythology for the Medici family when he became duke in 1537 – even before he catapulted to grand dukedom in 1569. Cosimo fashioned himself an earthly embodiment of the cosmos, as his name implied. By this coup, he convinced the Florentine citizenry that it was Medici destiny to usurp power from the other prominent families who had long governed in uneasy coalition. As the head of his de facto dynasty, Cosimo I identified with the planet Jupiter, named after the king of the Roman pantheon, and he filled the Palazzo della Signoria, where he lived and ruled, with frescoes stressing this Olympic theme.

      Galileo had given Venice his telescope. Now he would offer Florence the moons of Jupiter.

      He quickly set down his discoveries in a new book, entitled Sidereus Nuncius, or The Starry Messenger. As he had done with his earlier work on the geometric compass, he dedicated the text to young Cosimo II. On this occasion, however, Galileo took the time and gave himself enough space properly to extol his prince:

      Your Highness…scarcely have the immortal graces of your soul begun to shine forth on Earth than bright stars offer themselves in the heavens which, like tongues, will speak of and celebrate your most excellent virtues for all time. Behold, therefore, four stars reserved for your illustrious name, and not of the common sort and multitude of the less notable fixed stars, but of the illustrious order of wandering stars, which, indeed, make their journeys and orbits with a marvellous speed around the star of Jupiter, the most noble of them all, with mutually different motions, like children of the same family, while meanwhile all together, in mutual harmony, complete their great revolutions every twelve years about the centre of the world…

      Indeed, it appears that the Maker of the Stars himself, by clear arguments, admonished me to call these new planets by the illustrious name of Your Highness before all others. For as these stars, like the offspring worthy of Jupiter, never depart from his side except for the smallest distance, so who does not know the clemency, the gentleness of spirit, the agreeableness of manners, the splendour of the royal blood, the majesty in actions, and the breadth of authority and rule over others, all of which qualities find a domicile and exaltation for themselves in Your Highness? Who, I say, does not know that all these emanate from the most benign star of Jupiter, after God the source of all good? It was Jupiter, I say, who at Your Highness’s birth, having already passed through the murky vapours of the horizon, and occupying the midheaven and illuminating the eastern angle from his royal house, looked down upon Your most fortunate birth from that sublime throne and poured out all his splendour and grandeur into the most pure air, so that with its first breath Your tender little body and Your soul, already decorated by God with noble ornaments, could drink in this universal power and authority.

      In the continuing paean of the remaining paragraphs of this dedicatory note, Galileo took it upon himself to name the planets the Cosmian stars. But Cosimo, the eldest of eight siblings, preferred the name Medicean stars – one apiece for him and each of his three brothers. Galileo naturally bowed to this wish, though he was thus forced to paste small pieces of paper with the necessary correction over the already printed first pages in most of the 550 copies of The Starry Messenger.

      The book created a furore. It sold out within a week of publication, so that Galileo secured only six of the thirty copies he had been promised by the printer, while news of its contents quickly spread worldwide.

      Within hours after The Starry Messenger came off the press in Venice on 12 March 1610, the British ambassador there, Sir Henry Wotton, dispatched a copy home to King James I. ‘I send herewith unto His Majesty’, the ambassador wrote in his covering letter to the earl of Salisbury,

      the strangest piece of news (as I may justly call it) that he hath ever yet received from any part of the world; which is the annexed book (come abroad this very day) of the Mathematical Professor at Padua, who by the help of an optical instrument (which both enlargeth and approximateth the object) invented first in Flanders, and bettered by himself, hath discovered four new planets rolling about the sphere of Jupiter, besides many other unknown fixed stars; likewise, the true cause of the Via Lactea [Milky Way], so long searched; and lastly, that the moon is not spherical, but endued with many prominences, and, which is of all the strangest, illuminated with the solar light by reflection from the body of the earth, as he seemeth to say. So as upon the whole subject he hath first overthrown all former astronomy – for we must have a new sphere to save the appearances – and next all astrology. For the virtue of these new planets must needs vary the judicial part, and why may there not yet be more? These things I have been bold thus to discourse unto your Lordship, whereof here all corners are full. And the author runneth a fortune to be either exceeding famous or exceeding ridiculous. By the next ship your Lordship shall receive from me one of the above instruments, as it is bettered by this man.

      In Prague, the highly respected Johannes Kepler, imperial astronomer to Rudolf II, read the emperor’s copy of the book and leaped to judgment – despite the lack of a good telescope that could confirm Galileo’s findings. ‘I may perhaps seem rash in accepting your claims so readily with no support of my own experience,’ Kepler wrote to Galileo. ‘But why should I not believe a most learned mathematician, whose very style attests the soundness of his judgment?’

      The copy of The Starry Messenger that had the greatest impact on Galileo’s life, however, was the one he sent to Cosimo, along with his own superior telescope. The prince expressed his thanks late in the spring of 1610 by appointing Galileo ‘Chief Mathematician of the University of Pisa and Philosopher and Mathematician to the Grand Duke’. Galileo had specifically stipulated the addition of ‘Philosopher’ to his title, giving himself greater prestige, but he insisted on maintaining ‘Mathematician’ as well, for he intended to prove the importance of mathematics in natural philosophy.

      In negotiating his Tuscan future, Galileo requested the same salary he had recently been promised by the University of Padua – the figure of one thousand to be paid now in Florentine scudi instead of Venetian florins. Rather than plead for more money, he made the base pay stretch further by seeking official release from responsibility for his brother’s share of their sisters’ dowries.

      Galileo also secured a bonus in personal liberty by arranging for his university appointment at Pisa to entail no noisome teaching duties. He would be free to study the world around him for the rest of his days, and to publish his discoveries for the benefit of the public under the protection of the grand duke, who promised to pay for the construction of new telescopes.

       [IV] To have the truth seen and recognised

      NINE-YEAR-OLD LIVIA rode south with her father when he moved to Florence to assume his new court post in September of 1610. They left behind the serpentine canals of Venice, where the doge’s palace brushed the water’s edge like a fantasy spun from pink sugar and meringue. They crossed the fertile Po Valley and the Apennine spine of the Italian peninsula