Galileo

by Mario Livio

  Put simply, Galileo argued—albeit only privately—that the meaning in the case of Abraham’s sons or Tobias’s dog is obviously literal, and therefore believing it (or not) could be taken to be a matter of faith, while the stability of the Earth is only figurative and hence not a matter of faith. There is little doubt that Galileo chose the example of Tobias’s insignificant dog as something that is totally inconsequential in religious matters.

  Galileo would later answer attempts to prohibit any revisions to interpretations of Scripture with a quote from renowned ecclesiastical historian Cardinal Cesare Baronio, who died in 1606: “The intention of the Holy Spirit is to teach us how one goes to heaven and not how heaven goes.” With a not so subtle jab at Bellarmino’s letter to Foscarini, Galileo added that he had doubts “whether it is true that the Church obliges one to hold as articles of faith such conclusions about natural phenomena” and that he believed that “it may be that those who think in this manner may want to amplify the decree of the Councils in favor of their own opinion” [emphasis added]. Indeed, a few of Bellarmino’s eventual actions, or, rather, lack thereof, when the decree of the Congregation of the Index against Copernicanism was published on March 5, 1616, showed that he was in agreement with that decision.

  This tumult was not encouraging. In spite of Foscarini’s honest motives and thoughtful arguments, his book attracted more scrutiny to the Copernican issue, and that, combined with the damaging acts of Caccini, delle Colombe, and Lorini, generated an atmosphere in which the specter of a condemnation of Copernicanism by the Church was rapidly becoming a reality. To counter that disconcerting trend, Galileo composed his Letter to the Grand Duchess Christina, which was a powerful document defending the autonomy of scientific research. However, probably realizing the danger of his situation, Galileo prudently refrained from circulating yet another polemic. Instead, he decided to go to Rome to present his case in person, contrary to the advice of his friends there, all of whom suggested to postpone such a visit and “to be quiet.” The Tuscan ambassador to Rome, Piero Guicciardini, was especially displeased with Galileo’s plan, noting that “this is no fit place to argue about the Moon, or, especially in these times, to try to bring in new ideas.” It goes without saying that this attempt at dissuading Galileo, who always believed in his power of persuasion, also fell on deaf ears, and he arrived in Rome on December 11, 1615.

  CHAPTER 7 This Proposition Is Foolish and Absurd

  In Rome, Galileo was starting to realize the magnitude of the opposition he was facing. It was rapidly becoming apparent that what was badly needed was a clear demonstration or proof of the Earth’s motion. Sensing that, Galileo formulated in January 1616 a theory of ocean tides, which may have been based on earlier ideas of his friend Paolo Sarpi. He outlined the theory in a letter entitled Discourse on the Tides, which he sent on January 8 to a very young cardinal, Alessandro Orsini, who was to become Galileo’s supporter.

  Galileo’s theory of the tides must have sprung, at some level at least, from his or Sarpi’s observations of water sloshing back and forth at the bottom of a barge on his trips from Padua to Venice. He noticed that when the barge was accelerating, water piled up at the back, and when it slowed down, it accumulated at the front. This to-and-fro motion, Galileo thought, resembled the tides. It then occurred to him that in the case of the Earth, the speeding up could be the result of the diurnal spin motion being in the same direction and combining with the velocity of the Earth in its revolution around the Sun, which happens once a day at a given point on the Earth’s surface, as in point A in Figure 7.1. The slowing down, in this picture, occurs (again, once a day) when the velocities associated with the orbital motion and with the spin are in opposite directions (as in point B in Figure 7.1). The continents were assumed not to be dislocated by the combinations of these two motions, but the oceans were supposed to respond by sloshing. Galileo was therefore convinced that in the absence of even one of these two motions, “the ebb and flow of the oceans could not occur.”

  Unfortunately, in spite of the fact that Galileo thought that he had elegantly associated the Earth’s motion with the tides, “taking the former as the cause of the latter, and the latter as a sign of and an argument for the former,” his theory of the tides was neither correct nor convincing. The Earth’s revolution around the Sun played a rather subordinate role in it, and it certainly couldn’t explain actual observations of tides in the Adriatic Sea, where local conditions and secondary causes produced significant effects. The theory did conform to Galileo’s general tendency to exclude the action of unseen forces acting across large distances, such as the gravitational attraction of the Moon, even though ideas along those lines had existed since antiquity, and the Flemish mathematician Simon Stevin, as well as Kepler, specifically suggested the Moon’s attraction as the cause of the tides in 1608 and 1609, respectively. Albeit wrong, Galileo’s commitment to mechanically easy-to-understand causation made his theory of tides at least plausible. Newton eventually used his theory of gravitation to explain in detail how the combined action of the gravity of the Moon and the Sun provides the tide-generating forces.

  Figure 7.1. Schematic demonstrating Galileo’s theory of tides.

  In an attempt to persuade a few of his adversaries, Galileo met with Caccini at the beginning of February 1616, but he did not succeed in appeasing him or in convincing him to change his views. He also discovered a new opponent, Monsignor Francesco Ingoli, who in January 1616 wrote an essay entitled “Disputation concerning the Location and rest of Earth against the system of Copernicus,” and who was to become an active anti-Copernican.

  Things took a turn for the worse when on February 19 the theologian consultors to the Holy Office were asked to give their opinion on two propositions: (1) The Sun is the center of the world and completely devoid of local motion, and (2) the Earth is not the center of the world, and not motionless—it moves as a whole of itself, and also with a diurnal rotational motion. Ironically, the same office that had objected vehemently to scientists intruding into theology was now asking the theologians to judge on two purely scientific questions—two of the central tenets of the Copernican model.

  The consultors included the archbishop of Armagh, Ireland, the master of the Sacred Apostolic Palace, the Commissary of the Holy Office, and eight other religious figures, most of them Dominicans. Not one was a professional astronomer or even an accomplished scientist in any discipline. They took only four days to give their collective opinion. On the Sun being at the center of the solar system and motionless, they concluded that “this proposition is foolish and absurd in philosophy, and formally heretical, since it explicitly contradicts in many places the sense of Holy Scripture.” They were slightly less harsh and more tentative on the second proposition, since the Bible doesn’t say explicitly that the Earth does not move. Therefore, they concluded that “the proposition receives the same judgment in philosophy and that in regard to the theological truth, it is at least erroneous in faith.” That is, they replaced the categorical “formally heretical” with “at least erroneous in faith.”

  Events then followed in rapid succession. Pope Paul V met with his cardinals on February 24. The freshly appointed Cardinal Alessandro Orsini, who was related to the Medicis through his mother, tried to argue in Galileo’s defense and to present the scientist’s theory of the tides. Orsini was greatly impressed with Galileo’s arguments in a long conversation the two held about two months earlier. Unfortunately, he was cut short and promptly instructed by the Pope to convince Galileo to abandon his Copernican views. On the twenty-fifth, the Pope ordered Cardinal Bellarmino to summon Galileo and to warn him to renounce the opinion that the Sun stands still and the Earth is in motion. He added that refusal to obey the order would result in imprisonment. Bellarmino and Galileo met on February 26 in Bellarmino’s chambers, in the presence of Michelangelo Seghizzi, the Commissary General of the Holy Office, and two other church functionaries from the cardinal’s household. A document recorded
by a clerk, summarizing what transpired at that meeting, became the centerpiece of the evidence at Galileo’s trial seventeen years later:

  At the palace of the usual residence of the said Most Illustrious Lord Cardinal Bellarmino and in the chambers of His Most Illustrious Lordship, and fully in the presence of the Reverend Father Michelangelo Seghizzi of Lodi, O. P. and Commissary General of the Holy Office, having summoned the above-mentioned Galileo before himself, the same Most Illustrious Lord Cardinal warned Galileo that the above-mentioned opinion was erroneous and that he should abandon it; and thereafter, indeed immediately, before me and witnesses, the Most Illustrious Lord Cardinal himself being also present still, the aforesaid Father Commissary, in the name of His Holiness the Pope and the whole Congregation of the Holy Office, ordered and enjoined the said Galileo, who was himself still present, to abandon completely the above-mentioned opinion that the sun stands still at the center of the world and the earth moves, and henceforth not to hold, teach, or defend it in any way whatever, either orally or in writing; otherwise the Holy Office would start proceedings against him. The same Galileo acquiesced in this injunction and promised to obey.

  A second document describing what took place comes from the minutes of the meeting of the Holy Office on March 3. The account there reads: “The Most Illustrious Lord Cardinal Bellarmino having given the report that the mathematician Galileo Galilei had acquiesced when warned of the order of the Holy Congregation to abandon the opinion which he held till then, to the effect that the sun stands still at the center of the spheres but the earth is in motion.”

  The fact that the two documents, written on separate dates, contained some small but significant differences has generated much speculation among Galileo scholars. In particular, the meaning of the phrase “and thereafter, indeed immediately” in the first document is unclear. Was Galileo allowed to react to Bellarmino’s initial admonition? If not, then there were no grounds for the Commissary General’s injunction. If, as the second account seems to imply, Galileo promised to obey already after Bellarmino’s warning, then, again, there was no reason for Seghizzi to intervene and impose a much more severe injunction (including not to “teach, or defend in any way whatever”). If one adopts a less conspiratorial interpretation, then the impression one gets is that maybe upon hearing Bellarmino’s unexpected warning, Galileo hesitated a bit in his initial reaction, and that this precipitated an unjustified intervention by the impatient commissary general, who presented the injunction in more uncompromising terms. At that point, Galileo had to yield, or be imprisoned.

  The Congregation of the Index also had to reach a decision as to what actions should be taken concerning publications related to the Copernican doctrine. The issue was again presented by Bellarmino, at meetings that took place at the beginning of March 1616. On March 5 the Congregation published its devastating decree:

  This Holy Congregation has also learned about the spreading and acceptance by many of the false Pythagorean doctrine, altogether contrary to the Holy Scripture, that the earth moves and the sun is motionless, which is also taught by Nicolaus Copernicus’s On the Revolutions of the Heavenly Spheres and by Diego de Zúñiga’s On Job. [The latter, a commentary by the sixteenth-century Augustinian hermit, concluded that the Copernican system was in better agreement with the book of Job than the Ptolemaic one, and that “the mobility of the Earth is not against the Scripture.”] This may be seen from a certain letter published by a certain Carmelite Father, whose title is Letter of the Reverend Father Master Paolo Antonio Foscarini, Carmelite, on the Opinion of the Pythagoreans and of Copernicus Concerning the Mobility of the Earth and the Stability of the Sun and the New Pythagorean System of the World, etc., in which the said Father tried to show that the above-mentioned doctrine of the sun’s rest at the center of the world and the earth’s motion is consonant with the truth and does not contradict Holy Scripture. Therefore, in order that this opinion may not creep any further to the prejudice of Catholic truth, the Congregation has decided that the books of Nicolaus Copernicus (On the Revolutions of Spheres) and Diego de Zúñiga (On Job) be suspended until corrected; but that the book of the Carmelite Father Paolo Antonio Foscarini be completely prohibited and condemned; and that all other books which teach the same be likewise prohibited, according to whether with the present decree it prohibits and condemns, and suspends them respectively.

  At some level, the “good” news, from Galileo’s perspective, was that he had not been mentioned by name, nor had his publications been criticized in the decree. Nevertheless, just one day before the decree’s publication, the Tuscan ambassador, Guicciardini—who had previously advised against Galileo’s visit to Rome—sent a letter to the grand duke with a strong “I told you so” tone: “He [Galileo] is all afire on his opinions and puts great passion in them, and not enough strength and prudence in controlling them; so that the Roman climate is getting very dangerous for him, and especially in this century, for the present Pope, who abhors the liberal arts and this kind of mind, cannot stand these novelties and subtleties; and everyone here tries to adjust his mind and his nature to that of the ruler.” Simply put, Galileo received his first serious warning at the time of the strongly anti-intellectual Pope Paul V.

  One can hardly miss the similarity between Guicciardini’s description of the pervading mood in Rome of 1616 and that of today, replacing the word Pope with the appropriate current ruler who “abhors the liberal arts” and who “cannot stand these novelties and subtleties.” This raises the critical question of whether freedom of thought, and decision-making based on informed, evidence-based reasoning, are sufficiently strong at present, so as to prevent both catastrophic consequences and modern versions of the Galileo affair from reoccurring. Unfortunately, history has shown that the practice of denying science because of one’s beliefs has been repeated many times, even in the secular world.

  Galileo was trying to make the best of a horrible situation by pointing out in a letter to the secretary of state to the grand duke that he believed that the changes to Copernicus’s book would be minimal. In reality, the modifications introduced by Cardinal Luigi Caetani and later by Cardinal Francesco Ingoli were indeed relatively minor, and the publication of the revised version was approved in 1620. However, the new edition never reached the press, and so Copernicus’s book remained on the Index of Prohibited Books until 1835! Nevertheless, Galileo was apparently correct in his assessment that, relatively speaking, the decree would not affect him too adversely, at least initially. In fact, he received an audience with the Pope just a week after the decree’s publication, and the pontiff promised him that he could feel safe for as long as the Pope lived. Even more important, in the wake of circulating rumors that the Church had imposed on Galileo severe atonements, self-abasement, and abjuration of his Copernican ideas, Cardinal Bellarmino issued a quite remarkable letter on May 26, 1616, in which he affirmed the following:

  We, Roberto Cardinal Bellarmino, have heard that Mr. Galileo Galilei is being slandered or alleged to have abjured in our hands and also to have been given salutary penances for this. Having been sought about the truth of the matter, we say that the above-mentioned Galileo has not abjured in our hands, or in the hands of others here in Rome, or anywhere else that we know, any opinion or doctrine of his; nor has he received any penances, salutary or otherwise. On the contrary, he has only been notified of the declaration made by the Holy Father and published by the Sacred Congregation of the Index, whose content is that the doctrine attributed to Copernicus (that the earth moves around the sun and the sun stands at the center of the world without moving east to west) is contrary to Holy Scripture and therefore cannot be defended or held.

  Obviously, Galileo was pleased with this document, and seventeen years later, he relied heavily on it for his defense when he was put on trial by the Inquisition. Nonetheless, we shouldn’t get carried away appreciating Bellarmino for writing this favorable letter. While the cardinal was certainly not the person who decided t
he Church’s view of Copernicanism, the fact remains that he did not object to the decree. Moreover, in spite of his seemingly moderate tone in his response to Foscarini, he did not argue (or at least did not do enough to convince the Congregation) to delay or postpone the decree until more observational evidence could be gathered, to avoid premature judgment. The net result of this lack of action on the part of Bellarmino and of all the mathematicians of the Collegio Romano—who had confirmed all of Galileo’s findings—was an erroneous, ill-considered decision. The ruling was made by officers of the Church for whom retaining authoritative power over areas totally outside their expertise took priority over open-minded critical thinking informed by scientific evidence. Sadly, we don’t lack modern-day equivalents.