Galileo

by Mario Livio

  When all was said and done, Galileo’s main goal in The Assayer was, from the outset, to destroy Tycho’s scenario, which he regarded as the only remaining obstacle to convincing everybody of the truth of the heliocentric model. Indeed, in his Balance, Grassi (speaking as Sarsi) defended his use of Tycho’s parallax argument:

  Let it be granted that my master followed Tycho. Is this such a crime? Whom instead should he follow? Ptolemy? Whose followers’ throats are threatened by the out-thrust sword of Mars now made closer. Copernicus? But he who is pious will rather call everyone away from him and will spurn and reject his recently condemned hypothesis. Therefore, Tycho remains as the only one whom we may approve of as our leader among the unknown course of the stars.

  The point about Copernicus was a pitiable argument to bring into a scientific debate—one that demonstrated precisely how convictions entirely irrelevant to the subject matter could color and distort opinions. Grassi relied here on the nonscientific 1616 decree against Copernicanism to argue that one couldn’t even consider the Copernican model of the solar system. Unfortunately, similar attitudes continue to sometimes dominate thought to this very day. A policy today that encourages the teaching of creationism as thinly veiled “intelligent design,” for instance, in order to steer students’ minds away from Darwin’s theory of evolution, amounts to precisely the same practice.

  This is not to say that Galileo was always right. In fact, as I noted earlier, his specific arguments about comets contained two glaring inconsistencies: one, in claiming that parallaxes couldn’t be used for comets—only to then turn around and use them to determine the distance to comets; and the other, in suggesting that comets move along a straight line—only to admit later that, in fact, they don’t. These were scientific errors that Grassi correctly pointed out and criticized. Science is not infallible. On the contrary, Galileo himself recognized that every scientific theory is subject to confirmation. What only science can promise, however, is a continuous, midcourse self-correction, as additional experimental and observational evidence accumulates, and new theoretical ideas (all based on mathematics, Galileo believed) emerge. Even with all his understandable caution to avoid being accused of Copernicanism, Galileo couldn’t abandon his trust in the burgeoning scientific method, insisting that philosophers should also use “natural reason, when one can,” to demonstrate the “falseness of those propositions which are declared to be against Holy Scripture.”

  As could be expected, The Assayer was received rather dissimilarly by Galileo’s Roman friends than by Grassi. The latter reportedly rushed to the Sun bookshop, where the first copy had been on display, emerging with a “changed color,” the book under his arm. Pope Urban VIII, on the other hand, apparently enjoyed The Assayer’s aggressive satire and pointed sarcasm, since he had it read at his table for entertainment.

  Grassi, keen on publishing a reply, wrote a new book relatively rapidly (still using the pseudonym Sarsi), entitled Comparison of the Weights of the Balance and The Assayer.” Aware of the Pope’s support for Galileo’s book, however, he published his book in Paris, which caused a considerable delay in its becoming available. Galileo read Comparison but decided that it would be a waste of time to respond yet again, even though the book did contain one worrisome innuendo. The insinuation concerned Galileo’s remarks on the subjective nature of qualities such as taste, smell, and color. Grassi claimed that this description went against the Catholic doctrine of the miracle of the Eucharist, which required the preservation of the taste and smell of the bread and the wine, even though their substance was transformed in a way beyond human comprehension into Christ’s body, blood, and soul.

  Italian scholar Pietro Redondi discovered and published in 1983 a previously unknown document in the archives of the Holy Office. This document, which Redondi attributed to Grassi, denounced Galileo as a heretic. In this new twist, the accusation was based on the fact that Galileo “openly declares himself a follower of the school of [ancient Greece philosophers] Democritus and Epicurus”—meaning that he believes in atoms—a belief that was considered incompatible with the trans-substantiation underlying the dogma of the Eucharist. From this letter, Redondi developed an imaginative conspiracy theory contending that the real heresy for which Galileo was eventually condemned was not Copernicanism but, rather, atomism. While most fellow historians do not accept Redondi’s speculation, there is no doubt that the addition of one more item to Galileo’s growing list of troubles certainly did not help.

  The bottom line was that in spite of the Pope’s apparent support and some reassurances from Father Niccolò Riccardi that Galileo’s opinions “were not otherwise against the Faith,” Galileo felt that he still had serious reasons to be concerned. With respect to atomism, today we believe that all ordinary matter is composed of some elementary particles that are not composed of other particles. In the extremely successful Standard Model of particle physics, those elementary particles include quarks (of which protons and neutrons are made), leptons (electrons, muons, and neutrinos), gauge bosons (force carriers), and the Higgs boson (which is an excitation of a certain field). Everyday matter is indeed composed of atoms, once presumed to be elementary but known today to contain those subatomic elementary particles.

  All the worries, anxiety, and fears associated with Grassi’s attacks notwithstanding, the relative success of The Assayer must have given Galileo some satisfaction. His conviction in the correctness of the Copernican model was too strong for him to give it up at that stage.

  CHAPTER 10 The Dialogo

  The Assayer did not present Galileo at his best as a scientist. Rather, it showed him more as a magician with words and tricky logic, and demonstrated his brilliance and articulation as a debater. However, the election of Maffeo Barberini as Pope Urban VIII, resurrected Galileo’s hopes that he could perhaps change the Church’s position vis-à-vis Copernicanism. With this goal in mind, Galileo wanted to meet with the Pope as early as possible, but his poor health prevented him from traveling to Rome until the spring of 1624. Pope Urban graciously granted Galileo no fewer than a half dozen audiences and showed him great respect and generosity, but the practical results fell short of Galileo’s expectations. He emerged from those meetings realizing that in spite of the new Pontiff’s open-mindedness, Urban VIII was convinced that humans would never be able to comprehend the mysteries of the cosmos. To the Pope, irrespective of which theory of planetary motions scientists were to adopt, “we cannot limit the divine power and wisdom to this way.” Galileo’s views were, of course, very different. Nevertheless, he came out with the impression that he was allowed to present the Copernican model as a hypothesis and to show that on scientific grounds, at least, this conjecture explained the observations better than the Aristotelian-Ptolemaic systems. As he was about to find out, even this impression was inaccurate.

  Upon his return to Florence, Galileo decided to proceed step-by-step, first by answering Francesco Ingoli’s eight-year-old publication against Copernicanism. Ingoli was the person who “corrected” Copernicus’s book for the Congregation of the Index. Galileo’s tactic was to present himself as choosing not to be a Copernican “for higher motives” [that is, for being a pious Catholic] rather than for scientific reasons, even though science was the area in which he exposed Ingoli’s arguments as very weak if not downright false. This was a risky move, and upon Federico Cesi’s advice, the letter to Ingoli was never delivered because “Copernicus’s opinion is explicitly defended, and though it is clearly stated that this opinion is found false by means of a superior light,” Cesi estimated that there would be those who “will not believe that and will be up in arms again.” Galileo’s close friend was undoubtedly right, since other events unfavorable to Galileo were piling up around that time. Perhaps the most significant were the premature death of his great supporter Virginio Cesarini, and the fact that Cardinal Alessandro Orsini, a previously enthusiastic admirer of Galileo’s, had joined the Jesuit order and had become greatly influenced by Gali
leo’s sworn enemy Christoph Scheiner. In addition, Mario Guiducci informed Galileo that the Holy Office had received a proposal from an unidentified person to add The Assayer to the list of prohibited books because of its pro-Copernican contents.

  All of this did not stop Galileo from starting around 1626 to compose his next major book, the Dialogo, which originally was supposed to describe in detail his theory of the tides—a phenomenon he still regarded as the most convincing proof for the Earth’s motion. The work, however, progressed very slowly over the next three years and with prolonged interruptions caused sometimes by Galileo’s declining health and sometimes by his needing more data on tides. Somewhat surprisingly, perhaps, Galileo decided not to react in any substantial way (except for a disgruntled letter to Prince Paolo Orsini) to Scheiner’s massive work on sunspots, Rosa Ursina, published in 1630.

  By the time Galileo was putting the final touches on the Dialogo, Lady Luck appeared to show him some kindness: Father Niccolò Riccardi, who had glowingly commended The Assayer some years earlier, was appointed master of the Sacred Apostolic Palace in June 1629. With that title, Riccardi became the person who gives the final authorization to print. Consequently, Galileo’s friends were cautiously optimistic about being able to print the book in Rome. Castelli, who now had an appointment as a professor of mathematics at the University of Rome, wrote to Galileo that Ciampoli “holds as solid” that were Galileo to come to Rome with the work in hand, he would “overcome whatever difficulty” he might meet.

  Galileo arrived in Rome on May 3, 1630, and was received as an honored guest by the Tuscan ambassador, Francesco Niccolini, who had been appointed to this post in 1621. About two weeks later, he was granted an audience with Urban VIII. Undoubtedly the Pope reiterated his previous opinions about the need to treat Copernicanism merely as a hypothesis and his belief that the universe would always remain beyond human comprehension. Nevertheless, based on the Pope’s general demeanor and warmth, Galileo apparently convinced himself that the Pontiff would not object to the publication of what was to become the Dialogo.

  Galileo did fail, however, to appreciate two crucial facts. The first had to do with the sensitive political situation and psychological state of the Pope himself. Urban VIII, who was a genuine lover and patron of the arts, had spent money extravagantly during his papacy—a splurge culminating in the sumptuous Palazzo Barberini, a seventeenth-century palace in Rome. At the same time, he funded the construction of a variety of fortresses and other military endeavors, financially debilitating a pontificate perceived already as nepotistic and consumed with desires for earthly delights. In addition, the Thirty Years’ War had been raging for more than a decade, with no end in sight, and even Rome’s relations with France, a country that Urban VIII generally supported, had been somewhat strained by the uncompromising positions adopted by the influential French cardinal Armand Jean du Plessis Richelieu. All of these predicaments had turned Pope Urban VIII into a moody, capricious, and suspicious man who demanded absolute obedience on all fronts from all of those surrounding him.

  The second reality that Galileo failed to recognize fully was the level of hatred a few of his enemies harbored toward him and for new scientific ideas in general, and the cruel steps that they were prepared to take to bring about his downfall. This animosity manifested itself in an appalling incident during Galileo’s stay in Rome. The event went like this: the abbot of Saint Praxedes in Rome apparently published a horoscope predicting the imminent death of the Pope and of his nephew. Some of Galileo’s adversaries tried to pin the blame on Galileo, announcing:

  Here we have Galileo, who is a famous mathematician and astrologer, and he is trying to print a book in which he impugns many opinions held by the Jesuits. He has let it be known… that at the end of June we will have peace in Italy, and that a little afterwards Sir Taddeo and the Pope will die. The last point is supported by Caracioli Neapolitan, by Father Campanella, and by many written discourses, which treat the election of a new Pontiff, as if the See were vacant.

  Galileo, who knew how superstitious Pope Urban VIII was, had to react immediately and send word to the Pope denying any involvement in the affair. Fortunately, this particular vicious plot did not succeed, and the Pope assured Galileo that he was clear of any suspicion.

  Father Riccardi, who was in charge of approving the Dialogo, was perfectly aware of the delicate situation in Rome at the time. After his first reading of the manuscript, he realized at once that despite what Galileo might have thought, and even though the final result of the discussion was left inconclusive, this was, at least in large parts, an unmistakably pro-Copernican text, which could spell serious trouble if published unedited. He therefore suggested that, in addition to some necessary revisions, an introductory section or preface, and a concluding chapter be added, which would emphasize the hypothetical nature of the Copernican model. Consequently, it was decided that both Riccardi himself and the Dominican Raffaele Visconti would review the book thoroughly before discussing it with the Pope. That conversation with the Pontiff eventually took place in mid-June 1630, and based on what had been presented to him (which was partial at best), the Pope expressed his general satisfaction. He did insist, though, on the title to not concentrate on the tides—since that would have implied that the main topic was proof of the Earth’s motion—but on the “Chief World Systems.” With these assurances and a friendly parting from the Pope and his nephew Cardinal Francesco Barberini, Galileo finally departed for Florence on June 26, 1630.

  Unfortunately, this was not the end of the trials and tribulations Galileo had to endure for the publication of the Dialogo. Most significant of these was the sudden death on August 1, 1630, of Federico Cesi, the founder and sole source of funding for the Accademia dei Lincei. As a result, the printing had to be done in Florence, outside of Riccardi’s jurisdiction, instead of Rome. After some negotiations, it was agreed that Father Jacinto Stefani, a consultor to the Inquisition in Florence, would be in charge, but only after Riccardi approved the introduction and conclusion. The entire operation was painfully slow. Galileo, who by now had lost his forbearance, consented to a meeting with all the Florentine parties of authority involved, and he stated impatiently:

  “I agree to give the label of dreams, chimeras, misunderstandings, paralogisms, and conceits to all those reasons and arguments which the authorities regard as favoring opinions they hold to be untrue; they would also understand how true is my claim that on this topic I have never had any opinion or intention but that held by the holiest and most venerable Fathers and Doctors of the Holy Church.”

  To make a very long story short, the printing of the Dialogo wasn’t completed until February 21, 1632. The book listed the permissions (imprimatur) of both Riccardi and of the inquisitor in Florence, Clemente Egidi, even though Riccardi himself had not seen the final version but had sent the instructions about the introduction and ending to Egidi. Respecting the Pope’s request, the title read (not including various attributions) Dialogue Concerning the Two Chief Systems of the World, Ptolemaic and Copernican, Propounding Inconclusively in the Philosophical Reasons as Much for the One Side as for the Other (Figure 10.1 shows the title page). There was a certain sleight of hand in the title. Even if one were to ignore the fact that the Aristotelian and the Ptolemaic systems were not identical, there was at least one other world system that in terms of agreement with observations was superior to the Ptolemaic: Tycho Brahe’s hybrid system in which the planets revolved around the Sun, but the Sun itself revolved around the Earth. Galileo always regarded that system as unnecessarily complex and contrived, and he also thought that he’d found proof for the Earth’s motion through the phenomenon of the tides, so in striving to hand Copernicanism a clear victory (although formally the book was inconclusive), he probably didn’t want to confuse the issue with superfluous qualifications.

  Figure 10.1. Title page of the Dialogo.

  Figure 10.2. Frontispiece of the Dialogo.

  In the all-important
preface—added at Father Riccardi’s request in order to assist in obtaining permission to print—Galileo did his best to give the impression that he agreed with the 1616 anti-Copernican decree. Readers today may perceive that he barely succeeded in hiding his sarcasm and contempt for the decree and for the anti-intellectual constraints imposed on him personally:

  There were those who impudently asserted that this decree had its origin not in judicious inquiry, but in passion none too well informed. Complaints were to be heard that advisors who were totally unskilled at astronomical observations ought not to clip the wings of reflective intellects by means of rash prohibitions.

  Upon hearing such carping insolence, my zeal could not be contained. Being thoroughly informed about that prudent determination, I decided to appear openly in the theater of the world as a witness of the sober truth. I was at that time in Rome; I was not only received by the most eminent prelates of that Court, but had their applause; indeed, this decree was not published without some previous notice of it having been given to me [by Cardinal Bellarmino].

  To further please the Pope, Galileo went against his personal scientific convictions and declared that with the Dialogo, he had “taken the Copernican side in the discourse, proceeding as with a pure mathematical hypothesis.” That is, he pretended to accept the “saving the appearances” approach to science. Finally, he also added a direct reference to the Pope’s view that even if the Copernican system explains the motions of the planets, it might not represent reality because God is all powerful and could have created the same appearance by some entirely different means, beyond human understanding. Along these lines, Galileo wrote: