by Mario Livio
Another person who immediately understood the value of Clavius’s support for the discoveries was Galileo’s friend the painter Cigoli. Having had the impression that Clavius regarded the discovery of Jupiter’s satellites as a hoax, he urged Galileo to visit Rome as soon as possible. This was sound advice, since Clavius was not the only person of authority in Rome who was skeptical. Christoph Grienberger, an Austrian Jesuit astronomer who eventually succeeded Clavius as professor of mathematics at the Collegio Romano, also suggested initially that Galileo’s mountains on the Moon were nothing more than fanciful imaginations and that Jupiter’s moons were merely optical illusions.
In the spring of 1610, many others were still equally incredulous. A fellow Florentine working in Venice at the time, Giovanni Bartoli, wrote on March 27: “They [the science professors] laugh at [these discoveries], and call them rash, while he [Galileo] tried to make them a great feat, and he has done so, and gained an increase in salary of 500 fiorentini.” Bartoli added that many of those professors “think that he [Galileo] has made fun of them when he gave out as a secret the common spyglass which is on sale in the street for four or five lire, of the same quality, it is said, as his.”
One more problem that Galileo faced was technical. Most of the telescopes circulating in Europe were either of very poor quality or difficult to use, and often both. This predicament was compounded by the fact that even with proper instruction, some people simply failed to see the phenomena that Galileo was claiming to have observed. As an example, when Galileo stopped at the University of Bologna on his way back to Padua from his meeting with the Grand Duke in Florence, he tried to demonstrate his findings to the chief astronomer there, Giovanni Antonio Magini—who, in 1588, had beaten Galileo to that post. Unfortunately, neither Magini nor anyone from his entourage succeeded in seeing Jupiter’s satellites, even though in Galileo’s own observation log, he recorded that on those two nights, April 25 and 26, he saw two and four moons, respectively.
Much worse yet, a Bohemian mathematician, Martin Horky, who at the time was working as an assistant to Magini and was even living in his home, wrote to Kepler a vicious letter describing Galileo’s visit, in which he stated scornfully: “Galileo Galilei, the mathematician of Padua, came to us in Bologna, and he brought with him that spyglass through which he sees four fictitious planets.” Horky added that he “tested that instrument of Galileo’s in innumerable ways” and that while “on Earth it works miracles, in the heavens it deceives, for other fixed stars appear double.” Horky went on to say that “most excellent men and most noble doctors” including philosopher Antonio Rofféni, “acknowledged that the instrument deceived.” Superfluously and brutally, Horky even included a description of Galileo’s physique, which, while probably partly accurate, given Galileo’s continuous battle with poor health, was also vitriolic: “His hair hung down; his skin, in its tiniest folds, is covered with marks of the mal français [syphilis]; his skull is affected, delirium fills his mind; his optic nerves are destroyed because he has scrutinized minutes and seconds around Jupiter with too much curiosity and presumption.… [H] is heart palpitates because he has sold everyone a celestial fable.”
Horky finished with a sentence in German, which, perhaps more than anything, revealed his treacherous character: “Unknown to anyone, I have made an impression of the spyglass in wax, and when God aids me in returning home, I want to make a much better spyglass than Galileo’s.”
As could perhaps be expected, Horky’s ambitions never materialized. His burning jealousy and fiery hatred toward Galileo, however, were not extinguished. In June he published in Modena, Italy, a tract entitled A Very Brief Pilgrimage Against the Sidereal Messenger Recently Sent to All Philosophers and Mathematicians by Galileo Galilei, which was really nothing more than a vicious diatribe against Galileo. Horky sought to deny the reality of Galileo’s discoveries, but his arguments were laughable. He further stated maliciously that the sole purpose of the points of light Galileo claimed to have seen near Jupiter was to satisfy Galileo’s lust for money.
While this particular incident backfired in a big way and ended well for Galileo—disgusted by Horky’s actions, Magini evicted him from his home, and Kepler had nothing to do with him anymore—Horky’s publication was symptomatic of the general reaction of adrenalized Aristotelian devotees.
AN OUTREACH CAMPAIGN
Galileo knew right away that he had a difficult persuasion battle on his hands, but he never shied away from polemics, and he was prepared to fight for what he strongly believed to be true. First and foremost, he had to convince his former pupil and future employer, the Grand Duke Cosimo II de’ Medici himself. To achieve this goal, he first dazzled the duke by showing him the spectacular views of the Moon through the telescope, probably as early as 1609. Later, he made sure that the duke would receive a high-quality telescope with detailed instructions on how to use it, as soon as The Sidereal Messenger hit the press in March 1610. Consequently, by the end of April, Galileo already knew that he could count on the duke’s support. He then had to consider whom it was most advantageous to win over next. Realizing shrewdly that he who pays the piper calls the tune, he decided to reach out to the patrons of scientists rather than to the scientists themselves. Accordingly, Galileo sketched out an incredibly ambitious outreach plan to the Tuscan court:
In order to maintain and increase the renown of these discoveries, it appears to me necessary… to have the truth seen and recognized… by as many people as possible. I have done and am doing this in Venice and Padua. [Galileo indeed gave three successful public lectures about his discoveries in Padua.] But spyglasses that are most exquisite and capable of showing all the observations are very rare, and among the sixty that I have made, at great cost and effort, I have been able to find only a very small number. [In fact, in the spring of 1610, he managed to have acceptable lenses for no more than about ten telescopes.] These few, however, I have planned to send to great princes, and in particular to the relatives of the Most Serene Grand Duke. And already I have been asked by the Most Serene Duke of Bavaria [Maximilian I, who employed Galileo’s brother Michelangelo as a lutenist] and the elector of Cologne [Ernest of Bavaria], and also by the Most Illustrious and Reverend Cardinal Del Monte [an important Venetian patron of Galileo], to whom I shall send [a spyglass] as soon as possible, together with the treatise. My desire would be to send them also to France, Spain, Poland, Austria, Mantua, Modena, Urbino, and wherever else it would please His Most Serene Highness.
A few others who, for obvious reasons, were on Galileo’s list of early recipients of the book and/or a telescope were various cardinals such as Scipione Borghese, who in addition to being a great patron of the arts was also the nephew of Pope Paul V, and Odoardo Farnese, another cardinal patron of the arts and the son of the Duke of Parma. Oddly enough, but not inconsistent with his character, Galileo’s focus was primarily on the success of his outreach program; so much so that he did not include his own brother Michelangelo among those who were to receive a telescope.
Fortunately for Galileo, the grand duke supported unequivocally the promotion efforts. Not only did the Tuscan court finance the manufacturing of all the necessary spyglasses, but also Tuscan ambassadors in the major European capitals were sent copies of The Sidereal Messenger and were charged with the task of helping to further Galileo’s discoveries. Why did the Medicis provide such indefatigable assistance to Galileo? Not because of their interest in the Copernican model, but because they recognized Galileo’s unusual ability and talent in presenting his discoveries as emblems of Medici power.
The endeavors started to bear fruit in April 1610. On April 19 Johannes Kepler, the most distinguished European astronomer at the time, delivered his ringing endorsement of Galileo’s findings. Amazingly, while Kepler had already read Galileo’s book, he offered his blessing and approval even before he had a chance to confirm the discoveries through his own observations: “I may perhaps seem rash in accepting your claims so readily with no su
pport of my own experience,” he wrote. “But why should I not believe a most learned mathematician, whose very style attests to the soundness of his judgment?” Then, in stark contrast to Horky’s charges of deceit, Kepler continued: “He has no intention of practicing deception in a bid for vulgar publicity, nor does he pretend to have seen what he has not seen.” Finally, describing the essential characteristics of a truly great scientist, Kepler pronounced: “Because he loves the truth, he does not hesitate to oppose even the most familiar opinion, and to bear the jeers of the crowd with equanimity.”
With respect to the observations themselves, Kepler made various speculations about the findings, some of them quite farfetched. For instance, he suggested that there were living beings on the Moon who constructed some of the observed features. In addition, since Kepler shared the prevalent religious belief that all cosmic phenomena must have a purpose, he reached the following imaginative deduction: “The conclusion is quite clear. Our Moon exists for us on the Earth, not for the other globes. Those four little moons exist for Jupiter, not for us. Each planet in turn, together with its occupants, is served by its own satellites. From this line of reasoning, we deduce with the highest degree of probability that Jupiter is inhabited.” Kepler did not know that Jupiter is a gas giant with no solid crust. The best chances for any form of life in the Jovian system are, in fact, on a couple of the moons.
Not all of Kepler’s inferences were so fanciful. For example, when discussing the fact that the fixed stars and the planets appeared differently when observed with the telescope, he made the following, astonishingly prescient remark: “What other conclusion shall we draw from this difference, Galileo, than that the fixed stars generate their light from within, whereas the planets, being opaque, are illuminated from without; that is, to use [philosopher Giordano] Bruno’s terms, the former are suns, the latter moons or earths?”
Today we indeed make the clear distinction between stars, which generate their own luminosity through internal nuclear reactions, and planets, which primarily reflect the light of their host stars.
In May 1610 Kepler published his letter under the title Dissertatio cum Nuncio Sidereo (Conversation with the Sidereal Messenger). Since Galileo was clearly pleased with its content, the letter was reprinted in Florence later in the year. At that point, praise started pouring in from all directions. Galileo was hailed as a Columbus of the heavens. The Scottish librarian Thomas Segeth raved: “Columbus gave man lands to conquer by bloodshed, Galileo new worlds harmful to none. Which is better?” Sir Henry Wotton, an English diplomat in Venice who managed to lay his hands on one of the very first scarce copies of The Sidereal Messenger, sent it to King James I of England on March 13, 1610, accompanied by a letter that read, in part: “I send herewith unto his Majesty the strangest piece of news… that he hath ever yet received from my part of the world; which is the annexed book… of the Mathematical Professor of Padua, who by the help of an optical instrument… hath discovered four new planets rolling about the sphere of Jupiter, beside many other unknown fixed stars.”
Another Englishman, astronomer Sir William Lower, who managed to hear about the discoveries in southwest Wales (testifying to the success of the outreach effort), sent on June 11, 1610, an even more enthusiastic letter to astronomer Thomas Harriot, saying: “Me thinkes my diligent Galileus hath done more in his threefold discoveries [referring to the mountains on the Moon, resolving the stars in the Milky Way, and Jupiter’s satellites] than Magellane [Portuguese explorer Ferdinand Magellan] in opening the streights to the South Sea or the duchmen that weare eaten by beares in Nova Zembla.” He was referring here to the Dutch navigator Willem Barentsz and his crew, who were stranded on the Arctic archipelago of Nova Zembla in 1596–97 while searching for a Northeast passage.
In France, at a commemoration held in the Loire Valley for the late King Henry IV on June 6, 1611, students recited a poem entitled “Sonnet on the Death of King Henry the Great, and on the Discovery of Some New Planets, or Stars Wandering Around Jupiter, Made This Year by Galileo Galilei, Famous Mathematician of the Grand Duke of Florence.” The king, stabbed to death a year earlier by a religious fanatic, had indeed shown keen interest in Galileo’s work, but never got to see the discoveries with his own eyes. His widow, Queen Marie de’ Medici (by then regent for her son, King Louis XIII), sent word to Florence requesting one of “Galilei’s large spyglasses.” Unfortunately, the first instrument delivered to her was not of a particularly high quality, reflecting Galileo’s difficulty in producing superior telescopes. Only in August 1611 was Galileo able to furnish the queen with an adequate spyglass, winning instant admiration. The grand ducal ambassador Matteo Botti wrote from France:
Having presented to Her Majesty the Queen your instrument, I showed her that it is much better than another one sent earlier.… Her Majesty liked it very much, and she even kneeled on the ground, in my presence, to see the Moon better. She enjoyed it infinitely and was very pleased by the compliment I offered her in your name, which was accompanied by much further praise, not only on my part but also on Her Majesty’s who demonstrates that she knows and admires you, as you deserve.
In Italy, the Medici commissioned poems about the discoveries from a number of Jesuit poets. Some of the excessively saccharine ones compared Galileo to Atlas, whose prowess forces even the heavens to turn on new stars. Venetian poet and glassmaker Girolamo Magagnati also wrote a few verses, in a pamphlet entitled A Poetic Meditation upon the Medici’s Planets, conveying the glorious merits of Galileo’s discoveries:
But you, O Galileo of the Ether, crossed
Boundless inaccessible fields,
And sank the curious plow
Of errant spirit into the eternal sapphires,
Turning over the Sky’s golden clouds
You discovered new Orbs and new Lights.
Perhaps the most impressive tribute was provided by Galileo’s friend the painter Cigoli, who was commissioned by Pope Paul V to create a fresco for the dome in the Pauline Chapel in the church of Santa Maria Maggiore. Assumption of the Virgin, executed between September 1610 and October 1612, depicted the Virgin standing on the Moon. The amazing element in this fresco was that Cigoli painted the Moon not as a smooth, spotless sphere, but rather precisely as it looked in Galileo’s drawings of what he saw through the telescope (Figure 5 in the color insert).
BELIEVE IN SCIENCE
In his epic poem The Aeneid, Virgil wrote: “Believe one who has proved it. Believe an expert.” Indeed, at some point, expert, professional confirmations of Galileo’s observations and findings started coming in from other astronomers, and once that happened, at least the validity of what this new Columbus of the night’s sky saw could no longer be questioned or disputed. During September 1610, both Kepler in Prague and Antonio Santini, a Venetian merchant and amateur astronomer, saw Jupiter’s satellites. Kepler used the telescope that Galileo had sent to Ernest of Bavaria, the elector-archbishop of Cologne, and Santini used a homemade telescope. Later in the fall, astronomer Thomas Harriot in England and astronomers Joseph Gaultier de La Valette and Nicolas-Claude Fabri de Peiresc in France also detected those four Medici moons. Astronomer Simon Mayr discovered them independently in Germany.
There remained the critically important opinion of the astronomers of the Collegio Romano, and of Clavius in particular. As late as October 1, 1610, Galileo’s friend Cigoli reported: “Clavius said to one of my friends about the four stars [Jupiter’s satellites] that he laughs at them, and that it will be necessary to make a spyglass which produces them and then show them, and that Galileo can keep his opinion, and he will keep his.” However, as the story of the new discoveries gained momentum and became a hot topic of discussion all across Europe, church officials could not fail to take notice of the potential implications for the Church’s orthodoxy. Consequently, the head of the Collegio Romano and chief theologian of the Holy Office (responsible for defending Catholic doctrine), Cardinal Roberto Bellarmino, asked the Jesuit mathemat
icians to specifically either confirm or refute five of Galileo’s findings: first, the multitude of fixed stars (in particular those observed in the Milky Way); second, that Saturn represented three conjoined stars; third, the phases of Venus; fourth, the rough surface of the Moon; and fifth, the four satellites of Jupiter.
The reason that Bellarmino’s first question concerned the reality of “a multitude of fixed stars” almost certainly had to do with disturbing memories related to the Giordano Bruno affair. Bruno’s assertion that the universe is infinite and harbors a huge ensemble of inhabited worlds was one of the reasons that had led to his condemnation and tragic fate. Bellarmino had participated in the proceedings of that condemnation. Galileo’s claimed discovery that the Milky Way was teeming with previously unseen stars undoubtedly gave Bellarmino a strong and unpleasant sense of déjà vu.
On March 24, 1611, Fathers Christopher Clavius, Giovanni Paolo Lembo, Odo van Maelcote, and Christoph Grienberger gave their answers: “It is true that with the spyglass very many wonderful stars appear in the nebulosities of Cancer and the Pleiades.” The mathematicians were a bit more cautious about the Milky Way, acknowledging that “it cannot be denied that… there are many minute stars” but noting that “it appears more probable that there are continuous denser parts.” As we know today, the Milky Way does contain in addition to the hundreds of billions of stars a disk of gas and dust. In the case of Saturn, the Jesuit mathematicians confirmed the oOo shape observed by Galileo, adding, “we have not seen the two starlets on either side sufficiently separated from the one in the middle to be able to say that they are distinct stars.” They fully confirmed the waning and waxing phases of Venus and the fact that “four stars go about Jupiter, which move very swiftly.” The only observation about which they had some reservations was that of the Moon. They wrote: