cphil_astro4
ASTRONOMY
CONTINUED
by Ray Shelton
Galileo Galilei was born at Pisa on February 15, 1564 in the same year that Michelangelo died and Shakespheare was born. He was born into an old and distinguished Florentine family whose name had been changed to Galilei five generation earlier in honor of a famous physician of the 13th century, Galileo. Galileo’s father, Vincenzio Galileo, was a cloth merchant who moved his family from Florence to Pisa in hope of more business. Vincenzio was an accomplished amateur musician, who in Florence belonged to a group musical radicals that wanted to overthrow the older forms of music and replace it with a new form of music. The group invented the recitative, a musical device still used in modern opera. Many historian of music credit this Florentine group with creating the opera. Vincenzio in 1581 published a very good book on musical theory entitled Dialogue on Ancient and Modern Music. Vencenzio taught his son music and drawing. He sent his son to an excellent Jesuit school at the Monastery of Vallambrosa near Florence. His father wanted his son to be a merchant and brought the boy home to Pisa; but in recognition of his son’s obvious gifts he sent him to the University of Pisa to study medicine. Vincenzio had five children to take care of (a younger son, Michelangelo, and three daughters), and tried to get him a poverty scholarship but Galileo was turned down. Galileo did not like the study of medicine which at that time was mainly the study of the classic texts of Aristotle and Galen. He soon got a reputation among his teachers as being extremely argumentative and sarcastic. Galileo showed remarkable mechanical ability. In 1582 during second year at the University, he discovered the fact that a pendulum of a given length swings at a constant frequency, regardless of its amplitude. He also invented a “pulsilogium”, a kind of metronome for measuring the pulse of patients. Galileo’s interest turned to mathematics and he left the University without a degree. Back home he received instruction in mathematics from Ostilio Ricci, a practical mathematician attached to the Tuscan court and not to the University. Galileo invented a hydrostatic balance and wrote a treatise on it, which he circulated in manuscript, and attracted the attention of the scholars. Among whom was Marchese Guidobaldo del Monte who recommended him to his brother-in-law Cardinal del Monte, who recommended him to Ferdinand de Medici, the Duke of Tuscany; as a result Galileo was appointed a lecturer in mathematics at the University of Pisa, four years after he left it for lack of funds. Thus at the age of twenty-five, he was launched on his academic career.
Four years later in 1592, Galileo was appointed to the vacant Chair of Mathematics at the famous University of Padua, 22 miles west of Venice, again due to the intervention of his patron, del Monte. Galileo remained at Padua for eighteen years. Here he laid the foundations of modern kinematics, the science of moving bodies, about which he published a book toward end of his life. Up to the age of forty-five, when he published the Messenger from the Stars in 1610, he had not published any scientific works. Through all these years, he not only taught, in his lectures, the old astronomy according to Ptolemy, but explicitly repudiated Copernicus. In a treatise which he wrote to be circulated among his students and friends, of which a manuscript copy, dated 1606, still survives, Galileo presents all the traditional arguments against the motion of the earth, that is, that the rotation of the earth would make it disintegrate, would leave the clouds behind, etc., etc. This contradicts what he claims in his letter to Kepler dated August 4, 1597, that he had “become an early convert to the opinions of Copernicus many years ago,” and that
“I have written many arguments in support of him and in refutation of the opposite view – which, however, so far I have not dared to bring into the public light, frightened by the fate of Copernicus himself, our teacher, who, though he acquired immortal fame with some, is yet to an infinite multitude of others (for such is the member of fools) an object of ridicule and derision.”
Thus he explains why he dared not make a public statement in support of Copernicus: he was frightened of becoming “an object of ridicule and derision”. And it would be another sixteen years after this letter to Kepler before Galileo would make his first explicit statement in favor of Copernicus in 1613, when Galileo was forty-nine years of age.
Kepler had sent a copy of his first book, the Cosmic Mystery, to Galileo and Galileo wrote the letter dated August 4, 1597, to thank him for it. The young Kepler was delighted with Galileo’s letter and on the first occasion when a traveler left Gratz for Italy he answered it. In the letter, dated October 13, 1597, Kepler exhorted Galileo to take a public stand: “Have faith, Galilii, and come forward! If my guess is right, there are few among the mathematicians of Europe who would wish to secede from us: for such is the force of Truth.” Galileo apparently took offense at Kepler’s exhortation, regarding it as an implied rebuke for cowardice. Galileo did not write to Kepler for next twelve years and never answered Kepler’s frequent requests for an opinion on his book, the Cosmic Mystery.
Galileo published his first scientific work in 1610, entitled Sidereus Nuncius, Star Messenger or Messenger from the Stars, in which he announced some of early observations of the heavens with the telescope which seemed to support the Copernican astronomy. Galileo started to use the telescope when he learned of the recent Dutch invention of it, while he was in Venice in the spring of 1609. Galileo did not invent the telescope. In September, 1608, a man at the annual fair in Frankfort offered a telescope for sale that had both a convex and a concave lens, and magnified seven times. On the October 2, 1608, the Dutch spectacle-maker Johann Lippershey of Middleburg claimed a license for thirty years from the Estates General of the Netherlands for the manufacturing of telescopes with single and double lens. In the following month, he sold several of these for 300 and 600 guilers each, but he was not granted an exclusive license because two other men had also claimed the same invention. Two of Lippershey’s instruments were sent as gifts by the Dutch government to the King of France; and in April, 1609, telescopes could be bought in the spectacle-makers’ shops in Paris. In the summer of 1609 Thomas Harriot in England made telescopic observations of the moon, and drew maps of the lunar surface. In the same year several of the Dutch instruments found their way to Italy and were copied there. Whether Galileo saw these Dutch instruments is not clear. Galileo himself in his Star Messenger says that he had only heard reports of the Dutch invention and that they had stimulated him to construct an instrument on the same principle “through deep study of the theory of refraction”. After he returned to Padua, he built a telescope of a magnifying power of three and quickly improved it to a power of 32. Because of the method that Galileo devised for checking the curvature of the lenses, his telescopes could be used for astronomical observation. They were soon in demand all over Europe. On August 8, 1609, Galileo invited the Venetian Senate to examine his spy-glass from the tower of St. Marco, with spectacular success. Three days later he made a present of it to the Senate, accompanied with a letter, explaining how important the instrument would be in war. The grateful Venetian Senate doubled his salary and made his professorship a life-long appointment at Padua (which belong to the Republic of Venice).
Not knowing of Thomas Harriot’s observations of the moon, Galileo claimed that he was the first person to use the telescope to study the heavens. He found the surface of the moon to be irregular and not a smooth, perfect sphere as was believed at that time. He found many more stars than could be observed by naked-eye; he observed that the Milky Way was composed of many individual stars. In addition to the three stars in the belt and the six in the sword in the constellation of Orion which can be seen by the naked-eye, Galileo found eighty adjacent stars; and to the seven in the Pleiades he found another thirty-six. In contrast to the fixed stars which appeared in the telescope as untwinkling points of light, the planets appeared as small disks of light about one minute of arc in diameter. He also discovered four of the satellites of Jupiter, which he thought were planets or stars and thus called them Sidera Medicea, “the Medicean Stars”, in honor of his former student and future employer, Cosimo II de Medici, soon to become the Fourth Grand Duke of Tuscany. Galileo published these observations in March of 1610 in Sidereus Nuncius. Whether at this time Galileo had already observed spots on the sun, the phases of Venus and what appeared to be three parts of Saturn, it is not clear from the Star Messenger. In his Star Messenger Galileo makes only one mention of the Copernican system. Referring to the four moons of Jupiter as four planets, he says:
“Moreover, we have an excellent and exceedingly clear argument to put to rest the scruples of those who can not tolerate the revolution of the planets about the sun in the Copernican system, but are so disturbed by the revolution of the single moon around the earth while both of them describe an annual orbit around the sun, that they consider this theory of the universe to be impossible.”
In other words, Galileo thought that the motion of the four moons about Jupiter invalidate of the anti-Copernicans arguments against the Copernican system. This is the only reference to Copernicus in the whole booklet and this reference contains no explicit commitment to the Copernican system. In fact the observations of Galileo recorded in the Star Messenger produce no clear arguments for the Copernican system and Galileo did not claim that they did. The one thing that it did show was that the heavenly bodies were not more perfect than the earth and that the earth was not unique in having a moon revolving around it. And it showed that the moon and the earth were similar, having valleys and mountains. The moons of Jupiter do not prove that Copernicus’ heliocentric system was right, but they did go a long way in showing that the earth was not the center around which every heavenly body in the universe revolve. But the impact of this small, very readable booklet was tremendous.
The booklet aroused immediate and passionate controversy. Copernicus’ Book of Revolutions or Kepler’s Cosmic Mystery had hardly caused a stir. The subject of the controversy was not the significance of the moons of Jupiter, but their existence. Some of Italy’s illustrious scholars flatly denied their existence. One of these was Galileo’s academic rival, Magini in Bologna. At a party held in a house in Bologna on April 24 and 25, 1610, a month after the publication of the Star Messenger, where Galileo was invited to demonstrate his spy-glass, not one of the numerous and illustrious guests present, including Magini, declared that they were convinced of the existence of Jupiter’s moons. Some refused to look into the telescope; others who did look said that they could not see them. When one of the former, Libri, who was professor at Padua, died soon after, Galileo made enemies by the sarcastic remark, “Libri did not choose to see my celestial trifles while he was on earth; perhaps he will do so now that he has gone to Heaven.” Those who did look and said that they couldn’t see them, were not just stubbornly denying what they were seeing, but really couldn’t see anything. Even though Galileo’s telescope was the best available, it was difficult to use having a clumsy mountings and no real eye-piece but a spectacle-sized lens. It took skill and experience to use it, something that few of the scholars possessed. As one remarked about Galileo, “the marvel is not so much that he found Jupiter’s moons, but that he was able to find Jupiter itself.” Some who looked said that what they saw were optical illusions, haloes, reflections from the clouds, or something produced by the device itself. And to compound the controversy Galileo himself could not explain how and why it worked in spite of his claim to understand the principles of refraction; the Star Messenger was strangely silent on this point. These arguments against the existence of Jupiter’s moon were asserted in a sensational pamphlet, Refutation of the Star Messenger, published by Magini’s young assistant, Martin Horky.
Kepler, when he received a copy of the Star Messenger from Galileo on April 8, 1610, although he did not have a telescope, accepted Galileo’s claims on trust and wrote by April 19 a short pamphlet in the form of an open letter entitled Conversation with the Star Messenger. It was published in Prague in May, 1610, and in Florence shortly afterward. Kepler publicly offered to serve in the battle for Truth as Galileo’s “squire” or “shield bearer.” And it was what Galileo needed and it turned the tide of astronomical opinion in his favor. Kepler’s authority as the Imperial Mathematician and as the first astronomer of Europe was uncontested. Although Galileo boasted about Kepler’s letter privately, he never thanked Kepler nor publicly acknowledged it.
Galileo’s reaction to Kepler’s offer of help was complete silence. Before Kepler had use of a telescope, when the Tuscan Ambassador to the Imperial Court, Julian de Medici, suggested that Galileo send a telescope to Kepler, he refused. The telescopes, which his workshop were turning out, were destined for various aristocratic patrons. Four months went by and when Martin Horky’s pamphlet appeared attacking the Star Messenger, the controversy over the moons of Jupiter reached its peak. So far no astronomer of repute had publicly confirmed the observation of the moons of Jupiter. Kepler’s friends began to reproach him for trusting Galileo. On August 9 Kepler wrote Galileo again asking him for a telescope so he can verify Galileo’s findings; and if not a telescope, the names of independent witnesses who can verifies his observations. This time Galileo wrote Kepler on August 19, apparently afraid of loosing a powerful ally. This was the second and last letter that Galileo wrote Kepler. In this letter Galileo refused to give or lend him a telescope and to name any witnesses; he offered himself as the only witness. The letter contained no report of any observations by Galileo and no mention of the important new discovery that he had recently made, which Galileo had communicated about a fortnight earlier to the Tuscan Ambassador, Julian de Medici, in Prague in the form of an anagram made up from the words describing the discovery: “SMAISMRMILMEPOETALEUMIBUNENUGTTAURIAS”.
The purpose of this meaningless sequence of letters was to safeguard Galileo’s priority to his discovery without disclosing what the nature of the discovery. The Tuscan Ambassador gave Kepler the anagram and Kepler tried to unravel it. Patiently he work on it; finally Kepler thought he had unscrambled it into what he himself described as “barbaric Latin verse”: “Salv umbistineum geminatum Martia proles” (“Hail, burning twin, offspring of Mars”). Accordingly Kepler thought that Galileo had also discovered moons around Mars. Three months later Galileo disclosed the solution, not to Kepler, but to the Holy Roman Emperor, Rudolph II: “Alissimum planetem tergeminum observavi” (“I have observed the highest planet [Saturn] in triplet form”). Kepler had missed the solution. Galileo was disclosing his observation about the planet Saturn, not Mars, that it had a three part form. His telescope was not strong enough to see clearly the rings about Saturn (which were only seen fifty years later by Christian Huygens) and that which he saw as two bumps on opposite sides of the planet, he interpreted as two moons. A month later Galileo sent another anagram again to Julian de Medici: “Haec immatura a me jam frustra leguntury” (“These immature things I am searching for now in vain”). Again Kepler tried to transpose the letters of the anagram, and after several frustrating attempts, in a letter to Galileo, he begged him to disclose the solution. And a month later Galileo disclosed the secret, again not directly to Kepler, but in a letter to Julian de Medici: “Cynthiae figuras aemulator mater amorum” (“The mother of love [Venus] emulates the shape of Cynthia [the moon]”. That is, in Galileo’s words, “Venus imitates the phases of the moon.” Galileo had discovered that Venus, like the moon, showed phases as it went through its 584 day cycle. This was a proof that Venus revolved about the Sun and not around the earth. Galileo thought that this proved the Copernican system; but he was mistaken; the phases of Venus also fitted into Tycho’s system.
Meanwhile, Kepler, using a telescope that was lent to him by one of his patrons, the Elector Ernest of Cologne, Duke of Bavaria, from August 3 to September 9, 1610, was able to see with his own eyes Jupiter’s moons and he published a short pamphlet, entitled Observation-Report on Jupiter’s Four Wandering Satellites, in which Kepler confirms with first-hand observations Galileo’s discoveries. The pamphlet was reprinted in Florence; it was the first public witness of independent, direct observation of the moons of Jupiter. Galileo never refers to this confirmation. In fact he rarely mentions Kepler in his works, except to refute him. Galileo ignored Kepler’s three laws of planetary motion, his work on optics and the Kepleran Telescope. Galileo to the end defended uniform circular motion on epicycles and deference on eccentrics as the only possible form of celestial motion.
Kepler’s support came at the right time; Galileo wanted to leave Padua to return to Tuscany and to be appointed Court Mathematician to Cosimo de Medici, the Grand Duke of Tuscany, in whose honor he had called the moons of Jupiter “the Medicean Stars.” He was home-sick for Tuscany and the position would give him more time for research. In the summer of 1610 Galileo took up his new position as “the first philosopher and mathematician” to the Grand Duke of Tuscany, at a large salary and unlimited time for research.
In 1611 Galileo visited Rome and demonstrated his telescope to the pontifical court. The visit was a triumph. The prestigious Accademia dei Lincei, presided over by the Prince Federico Cesi, elected him a member and gave him a banquet, at which the term “telescope” was first applied to his device. Pope Paul II gave him a friendly audience and the Jesuit Roman College honored him a whole day with various ceremonies. The astronomers and mathematicians of the College were entirely converted to the Copernican system, especially Father Clavius, the chief mathematician and astronomer, the principal author of the Gregorian Calendar reform, who had first laughed at the Messenger from the Stars. They had not only accepted Galileo’s observations, but they improved on them. When Lord Cardinal Bellarmine (1542-1621), the head of the College, ask their opinion of the discoveries, they unanimously confirmed them. The phases of Venus, in particular, were important; they were inconvertible proof that the planet Venus revolved around the Sun, that the Ptolemaic system was no longer tenable and the choice is now between Copernicus’ and Tycho Brahe’s systems. As the intellectual spearhead of The Roman Catholic Church, the Jesuit Order decided to support the Tychonic system as half-way house to Copernican system. The Copernican system itself could be freely discussed and used as a working hypothesis for computation; but it was not acceptable to present it as an established truth, since it was contrary to Scripture; unless and until a definite proof could be obtained, then and only then would Scripture have to be reinterpreted. This apparently was also the position of the Pope and the Roman Catholic Church.
But there was another powerful group in the Roman Catholic Church who did not take this position but completely rejected the Copernican and Tychonic systems in favor of the traditional Ptolemaic system: the Aristotelians in the universities. Following the Christian-Aristotelian theology of Thomas Aquinas, which was the official theology of the Roman Catholic Church since the Council of Trent (1545-1563), even though it said nothing against the heliocentric system of the universe, they interpreted Scripture as supporting the Ptolemaic system. Since, therefore, tradition and the Scriptures supported the Ptolemaic system, it was believed to be the unchanging, absolute truth. Thus these Aristotelian university professors rejected and attacked the astronomical views of Copernicus, Tycho, Kepler and Galileo as heresy. When one of Galileo’s favorite student, the Benedictine Father Castelli, the founder of modern hydrodynamics, was invited to the chair of the University of Pisa, he was expressly forbidden by the head of the University to teach the motion of the earth. The head was Arturo d’Elei, a fanatical Aristotelian and member of the “Pigeon League” (the name that Galileo and his friends called their opponents), who had published one of the pamphlets against the “Things that Float on Water.”
After his return from Rome to Florence, in the summer of 1611, Galileo became involved in several controversies; he had published a treatise on “Things that Float on Water.” Although having nothing to do with astronomy, in this pioneering work on modern science of hydrostatics, Galileo adopted Archimedes’ view that bodies float or sink according to their specific gravity, against the Aristotelian view that this depends on their shape. The Aristotelians interpreted this as a attack on them as well as their views. Galileo irritated them by making them look foolish in his arguments against their Aristotelian view. The leader of the Aristotelians was a certain Lodovico delle Colombe, meaning dove; hence Galileo and his friends referred to their opponents by the name “Pigeon League”. The controversy ended as a complete defeat of Galileo’s attackers; two of them, professors Palmerini and di Grazzia, died while Galileo was preparing his reply and Giorgio Coressio lost his chair at Pisa because he was discovered to adhere secretly to Greek Church and went insane. Coressio, not Galileo, was the one who had performed the famous experiment of dropping cannon balls from the leaning tower of Pisa, and, not to refute Galileo, but to confirm the Aristotelian view that larger bodies fall faster than smaller ones. Galileo never performed the experiment and the story that he did is a myth.
Being encouraged by the response in Rome, Galileo ventured in his Letters on Sunspots, printed in Rome in 1613, to make a brief public statement in favor of the Copernican theory. This occurred on the last page of the Letters on Sunspots, which Galileo wrote to claim priority for the discovery of them himself. He alleged that he had observed the sunspots for about eighteen months and to have shown them a year before “to many prelates and gentlemen in Rome,” but he did not give the names of any of them. But Galileo’s claim was untenable; the sunspots were discovered independently and at about the same time by Johannes Fabricius at Wittenberg, Thomas Harriot at Oxford, Father Scheiner and his young assistant, Cysat at Ingoldstadt in Bavaria, and Galileo himself. Harriot seems to have been first to see them, but Fabricius was the first to publish, then Scheiner the second. And Harriot, Fabricius and Scheiner neither knew of the other’s discovery nor claimed priority. When Father Scheiner and his young Cysat saw them, they wrote several letters to report their sensational discoveries to Marcus Welser at Augsberg. Welser promptly had the letters printed under the pseudonym, “Apples”, as Scheiner requested. Welser had the booklet sent to Kepler and to Galileo for their opinion. Kepler answered immediately, recalling that he had himself observed a sunspot in 1607, “of the size of a meager flea.” He said he had mistakenly thought that it was the planet Mercury passing in front of the Sun. Laughing at his mistake, Kepler goes on to cite reports of such observations going back to the time of Charlemagne; then he gives his opinion that the sunspots were a kind of dross, due to the cooling of Sun in patches. Galileo delayed his answer for more than four months. He argues convincingly that the sunspots are not due to planets passing front of the sun, as Scheiner had proposed, but that they were close or on the surface of the Sun; that they were rotating with the sun, constantly changing shape; that they were of nature of “vapors, exhalations, or clouds or fumes.” Thus the sun, like the moon, was subject to change and decay. Along with his claim of priority, this answer was included in his Letters on Sunspots with a veiled attack on the Jesuit Father Scheiner. Galileo seemed to have come think of himself as having an exclusive monopoly on telescopic discoveries, as he says later, “it was granted to me alone to discover all the new phenomena in the sky and nothing to anyone else.” The booklet was an immediate sensation and the Church did not raise any opposition. In fact the Cardinals, Boromeo and Barberini, who later became Pope Urban VIII, wrote letters expressing their sincere admiration.
The first serious attack on Galileo on religious grounds came, not from the religious authorities, but from a layman, the leader of the Pigeon League, delle Colombo. In his book Against the Motion of the Earth, he quotes a number of Scriptures to prove that the earth does not move. He circulated the book in manuscript form in 1610 and 1611, before Galileo made a public statement, and he does not mention Galileo by name. Galileo was apparently not worried about theological opposition since he waited for almost a year before he asked a friend of his, Cardinal Conti, for his opinion. The Cardinal gave his opinion that concerning the “immutability” of the heavens, the Scripture seemed to favor Galileo’s view, not Aristotle’s. As for Copernicus, the annual motion was admissible, but the daily rotation did not seem to agree with Scripture, unless it was assumed that certain passages of Scripture must not be taken literally; but such an interpretation was permissible “only in the case of necessity.” “Necessity” here meant, not logical necessity, but empirical necessity; that is, if and when convincing proof was given that the earth was really in motion. Until such proof was forth coming, the Copernican and Tychonic views could be freely discussed as mathematical hypotheses, not as fact, not as true.
There the matter would have stopped, except for Galileo’s hypersensitivity to criticism and uncontrollable urge to engage in controversy. Near the end of 1612, while he was staying in the vila near Florence, of his friend Filippo Salvatti, he heard some gossip that a Dominican Father, Niccolo Lorini, had attacked his views in a private conversation. He immediately wrote Lorini, asking for an explanation. Lorini wrote back denying the rumor, saying that at the dinner, not wanting to appear to be a blockhead, “I said, as I still say, that this opinion of Ipernicus – or whatever his name is – would appear to be hostile to divine Scripture. But it is of little consequence to me, for I have other things to do.” That was the end of that rumor. The next year, 1613, Galileo heard another piece of gossip, this time from Pisa, about an after-dinner conversation at Duke Cosimo’s table. Father Castelli, Professor of Mathematics at Pisa, the position that started Galileo’s career, had been invited for dinner at the Court. An illustrious company was present, including the Duke’s mother, the Dowager Duchess Christina of Lorraine and several other guests, among them Dr. Boscaglia, a professor of philosophy. A debate ensued over Galileo’s views. Father Castelli defended Galileo’s views against the Grand Duchess Christina arguments from Scripture, as he tells Galileo in a letter. In a later letter, Castelli reported that Boscaglia had once more been defeated in debate, that even the irascible Duchess had been won over, and that the subject had been dropped. Galileo was infuriated and he writes a counter-blast against the obscure Dr. Boscaglia in the form of a Letter to Castelli. He enlarged it a year later into a Letter to the Grand Duchess Christina. He intended that it should be widely circulated to silence all theological objections to Copernicanism. It was widely circulated but it had the opposite effect; it became the principal cause of the prohibition of Copernicus and the later downfall of Galileo.
As a piece of polemical literature the Letter to Castelli was a masterpiece. It starts by belittling the argument of his opponents, the academic philosophers, and assuming that the Copernican system had been proven true. Using an argument which Kepler constantly used, he argues that certain Scripture passages should not be taken literally because they are couched in language “according to the capacity of the common people who are rude and unlearned.” At the heart of his argument, he makes a distinction between physical propositions that are “soundly demonstrated” (that is, proven) and those that are “merely stated”. If propositions of the first kind contradict the apparent meaning of passages in the Bible, then the meaning of them must be reinterpreted, according to theological practice. So far he has stated correctly the attitude of the Roman Catholic Church. But Galileo continues:
“And as to the propositions which are stated but not rigorously demonstrated, anything contrary to the Bible involved by them must be undoubtedly false and should be proved so by every possible means.”
This was not the attitude of the Roman Catholic Church; “the propositions which are stated but not rigorously demonstrated,” such as the Copernican system, were not condemned outright, if they contradicted the Holy Scripture; they were treated as “working hypothesis” with the implied “wait and see” if they may be proven. But Galileo did not want to bear the burden of proof; he had no proof. He wanted it turned into a black and white alternative, that had to be accepted or condemned. The purpose of this sleight of hand becomes evident in the next sentence.
“Now if truly demonstrated physical conclusions need not be subordinated to biblical passages, but the latter must rather be shown not to interfere with the former, then before a physical proposition are condemned it must be shown to be not rigorously demonstrated and this is to be done not by those who hold the proposition to be true, but by those who judge it to be false. This seems very reasonable and natural, for those who believe an argument to be false may much more easily find the fallacies in it than men who consider it to be true and conclusive.”
Galileo had shifted the burden of proof. It is no longer Galileo’s task to prove the Copernican system, but the theologian’s task to prove it false. And if they don’t, their case goes by default and the Scripture must be reinterpreted. This was to hide the true status of Copernican system as a working hypothesis and that the burden of proof was upon those who believed that it was more that. The Roman Catholic Church had not condemned it, and neither did they have to prove it false. Throughout all of his writings, Galileo completely evaded any astronomical or physical data in support of the Copernican system; he simply gave the impression that the Copernican system had been proven beyond doubt. He had no irrefutable proof and that is what he had to hide. And when anyone would challenge him for the proof of the Copernican system he would attack the person making the challenge, belittling and ridiculing them. This kind of ad homimem argument would seem to win the immediate debate, but it makes lifelong enemies, and Galileo had made many of them this way.
In the final section of the Letter to the Grand Duchess, Galileo examines the miracle of the sun and moon standing still a whole day recorded in Joshua 10: 12-14. Galileo first explains his theory that the sun’s rotation is the cause of all planetary motion. So if the sun stopped rotating, all planetary motion would stop. Galileo, like Kepler, believed that, not only the annual revolution of planets about the sun was caused by the sun, but also their daily rotation on their axes. This was an ad hoc hypothesis for which there was no proof and was not a part of the Copernican system; in Copernicus’ system, as in the Ptolemaic system, God, the unmoved mover, moved the heavens. On the basis of this hypothesis, Galileo concluded that when Joshua commanded the Sun to stand still, the sun stopped rotating and as consequence both the annual and daily motion of earth stopped. The major objection to Galileo’s interpretation of this miracle is that, not only the motion of the earth would have stopped, but the motion of all the planets. But there are simpler interpretations of this miracle from within heliocentric system than Galileo’s; rejecting Galileo’s assumption that the motion of the planets are due to sun, only the daily motion of the earth would have to stop and not the whole solar system. Those who rejected the heliocentric Copernican system thought the interpretation of this miracle from within the Ptolemaic system was even simpler; since the sun was in motion rather than the earth, the command that the Sun stand still would mean that only the Sun would have stopped its motion. Of course Galileo rejected the Ptolemaic system as true. Galileo did not have to face objections to this miracle, but only to his interpretation of it, that if the earth suddenly stopped its motion, everything not attached to the earth would go flying off. Galileo would have realized this, having proposed in his Star Messenger the idea of inertia, and his explanation of it came close to the Law of Inertia; but he did not have to face this objection, since no one at that time was raising an objections to this miracles or miracles in general. Galileo did not reject this miracle. This miracle of the Sun standing still clearly implies the suspension of the Law of Inertia. But this is what a miracle really is: a suspension of natural laws.
For a whole year the Letter to Castelli was circulated and nothing happened. In December 1614, another Dominican Monk, Father Thommaso Caccini, who had been previously censured as a rabble-rouser, preached a sermon in the church of Santa Maria Novella in Florence in which he attacked mathematician in general and Copernicus in particular. Galileo promptly complained to Caccini’s superiors and the Preacher General of the Dominican order wrote Galileo an apology. At the same time as Caccini’s sermon, Father Lorini was shown a copy of the Letter to Castelli. He was deeply shocked and made a copy of it. Returning to his convent of St. Mark in Florence, he discussed its contents with his brethren and they came to the conclusion that the Letter should be forward to the Holy Office. On February 7, 1615, Father Lorini wrote to Cardinal Sfondrati a letter to accompany document. It did not mention Galileo by name, but referred to the writer as a Galileist, apparently not sure whether the writer was Galileo or Copernicus. Father Lorini wrote, “that they [the Galileist] strove to defend an opinion which appear contrary to the sacred text; that they spoke in slighting terms of the Fathers and of St. Thomas Aquinas; that they were treading underfoot the entire philosophy of Aristotle which has been of such service to Scholastic theology…” The Cardinal forward the Letter to Castelli to the Consultor of Holy Office for his opinion; he replied, although some of the words “such as ‘false’ and ‘perverting’ sound very bad”, considered in the general context, they did not deviate from Catholic doctrine; as for the remaining document they had no objections. The charges of Father Lorini was dismissed. A month later Caccini appeared in Rome, approaching the Holy Office “begging to testify concerning the errors of Galileo for the exoneration of his conscience.” The Inquisition heard him and, finding contradictions in his testimony, dismissed his charges against Galileo of heresy and of subversion of the faith in November, 1615.
Three months after all charges were dismissed against Galileo, on March 5, 1616, Copernicus’ book was placed on the Index of forbidden books, “pending corrections”. Galileo’s refusal to compromise and his insistence that the Copernican system accepted as true, not just as a working mathematical hypothesis, and that the Scripture must be reinterpreted accordingly, lead directly to this event. On February 16, 1616, Galileo sent of copy of Letter to Castelli to Cardinal Piero Dini, Archbishop of Fermo, with the request that it should be shown to Father Grienberger, who had been first among the leading astronomers in Rome to be converted by Galileo’s telescopic discoveries, and if possible to Cardinal Robert Bellarmine, a general of the Jesuit Order, Consultor of the Holy Office and “Master of Controversial Questions” at the Roman College. Before Dini could reply, Monsignor Giovanni Ciampoli wrote to Galileo at the end of February,
“Cardinal Barberini [the future Pope Urban VIII]… told me only yesterday evening that with respect to these opinions he would like greater caution in not going beyond the arguments used by Ptolemy and Copernicus, and finally in not exceeding the limitation of physics and mathematics. For to explain Scriptures is claimed by the theologians as their field, and if new things are brought in, even by an admirable mind, not everyone has the dispassionate faculty of taking them just as they are said.”
In other words, the Copernican system, as the Ptolemaic system was, should be regarded as a mathematical hypothesis only, in the sense of Osiander’s preface to Copernicus’ book. And that the interpretation of Scriptures was the province of the theologians, not of the physicists or of the mathematicians (or astronomers). A few days later on March 4, Galileo got Dini’s reply advising him to be cautious in these matters. Dini relays Bellarmine’s statement about the prohibition of Copernicus’ book that it might be until corrections are made “to the effect that Copernicus had introduced his theory in order to save the appearances, or some such thing – just as others had introduced epicycles without thereafter believing in their existence.” And that this fix would not require a reinterpretation of certain Scripture passages. On the same day, March 7, Galileo got a letter from Prince Cesti, the President of the Linecean Academy, telling him the sensational news that a Carmelite monk from Naples, Paolo Antionio Foscarini, a Provincial of his Order, had published a book in defense of Galileo and Copernicus. He reported that Foscarini was now in Rome and had offered to meet all comers in debate. Cesti said he had sent a copy of Foscarini’s book to Bellarmine. Then on March 21, Ciampoli relayed assurances to Galileo from Bellarmine that Galileo had nothing to fear so long as he kept to the province of physics and mathematics, and refrained from the theological interpretation of the Scriptures. Dini wrote again also warning Galileo in the same way, saying, “One may write freely as long as one keeps out of the sacristy.” Galileo answered these admonitions in a letter to Dini dated March 23. He said that he refused to compromise on the Copernican system and that Copernicus did not mean it to be understood just as a hypothesis, but to be accepted or rejected absolutely. He agreed that the interpretation of Holy Scriptures in light of the Copernican system should be left to the theologians. But he disagreed with Bellarmine interpretation of Psalm 19:5 passage that the sun “rejoiceth as a strong man to run his course.” Then in his letter to Dini, Galileo, as he says, “in all humility”, undertook to refute Bellarmine’s interpretation of the Psalm. Dini probably had enough wisdom not to show this to the greatest Roman Catholic theologian of the age.
Foscarini sent a copy of his book to Bellarmine, with an accompanying letter asking for his opinion. Bellarmine replied in a letter to Foscarini’s request and makes a precise and authoritative statement in view of his position as the Consultor to the Holy Office, Master of Controversial Questions, etc., and amounts to an unofficial statement of the Roman Catholic Church’s attitude concerning Copernicus. Although not addressed to Galileo, the letter applied to Galileo, since he is expressly mentioned by name. After a cordial introduction acknowledging Foscarini’s book and letter, he writes,
“First, I say it seems to me that your Reverence and Signor Galileo act prudently when you content yourselves with speaking hypothetically and not absolutely, as I have always understood that Copernicus spoke. For to say that the assumption that the Earth moves and the Sun stands still saves all the celestial appearances better than do eccentrics and epicycles is to speak with excellent good sense and to run no risk whatever. Such a manner of speaking suffices for mathematicians. But to want to affirm that the Sun, in very truth, is at the center of the universe and only rotates on its axis without traveling from east to west, and that the Earth is situated in the third sphere and revolves very swiftly around the Sun, is a very dangerous attitude and one calculated not only to arouse all Scholastic philosophers and theologians but also to injure our holy faith by contradicting the Scriptures …”
This passage of the letter makes clear that it was admissible, not only to expound the Copernican system, but also to say that the Copernican system is superior to the Ptolemaic system, as a hypothesis. But it would not be allowed to claim that the Copernican system is absolutely true. That would make it contradict the Scriptures. In the next section Bellarmine paraphrases the Council of Trent against the interpretation of Scriptures in ways contrary to tradition (which was directed against Luther and not Copernicus). In the third section Bellarmine states the condition which would justify an exception to the rule just stated.
“Third, I say that, if there were a real proof that the Sun is at the center of the universe, that the Earth is in the third sphere, and that the Sun does not go round the Earth but the Earth round the Sun, then we should have to proceed with circumspection in explaining passages of Scripture which appear to teach the contrary, and we should rather have to say that we did not understand them than to declare an opinion to be false which is proved to be true. But I do not think there is any such proof since none has been shown to me. To demonstrate that the appearances are saved by assuming that the sun is at the center and the earth in the heavens is not the same thing as to demonstrate that in fact the sun is the center and the earth is in the heavens. I believe that first demonstration may exist, but I have grave doubts about the second; and in case of doubt one may not abandon the Holy Scriptures as expounded by the holy Fathers.”
In other words, the new cosmology should be “really proven” (or “truly demonstrated”). Since no proof has been shown to him, he has “grave doubts” whether such proof exists; and in case of doubt the request for reinterpreting the Bible is rejected. Though Bellarmine does not say so, he probably consulted the astronomer Grienberger and Grienberger must have truthfully informed that there was no physical proof that the earth moved about the Sun. And he could have also told him that no stellar parallax had been observed and that would be in the nature of a disproof. The important point here with respect to Galileo is that Bellarmine put the burdened of proof back upon those who were advocating the Copernican system. Now there was only two possibilities left for Galileo: either to supply the required proof, or to agree to treat the Copernican system, for the time being, as a working hypothesis. Bellarmine had in a tactfully way reopened the door to this compromise in the first section in pretending that Galileo had contented himself in speaking hypothetically and not absolutely and in acting as though the Letter to Castelli and the Letter to the Grand Duchess did not exist. But Galileo was beyond compromise. For if he accepted the compromise, he would be disclosing to the world that he had no proof, and would be “laughed out of court”. He had to reject the compromise and insist that he had the proof; and that is what he decided to do. And since he did not really have the proof, he would have to pretend to have the proof, but refuse to produce it on the grounds that his opponents were too stupid to understand it. And he followed this strategy in his letter to Dini in May:
“To me, the surest and swiftest way to prove that the position of Copernicus is not contrary to Scripture would be to give a host of proofs that it is true and that the contrary cannot be maintained at all; thus, since no truths can contradict one another, this and the Bible must be perfectly harmonious. But how can I do this, and not be merely wasting my time, when those Peripatetics who must be convinced show themselves incapable of following the simplest and easiest of arguments? …”
But it is not the Aristotelian-Thomistic university professors that Galileo must convince but Bellarmine who had challenged him to produce the proof and he was not “incapable of following the simplest and easiest of arguments”. Galileo continues his letter after the section just quoted:
“Yet I should not dispair of overcoming even this difficulty if I were in a place where I could use my tongue instead of my pen; and if I ever get well again so that I can come to Rome, I shall do so, in the hope of at least showing my affection for the holy Church.”
Early in December he arrived in Rome and began to use his tongue instead of his pen. Father Grienberger had sent him word that it would be better to bring convincing scientific proof in support of Copernicus before trying to adjust Scripture to Copernicus. The Tuscan Ambassador in Rome, Guicciardini, had warned Duke Cosmo against Galileo coming to Rome, and Bellarmine, who saw the consequences, had also advised against it. But the Duke had given in to Galileo, and on his instructions Galileo had taken up residence in the Villa de Medici, then the Tuscan Embassy. Bellarmine was trying to keep Galileo away from Pope Paul V Borghese, who “abhors the liberal arts and his [Galileo’s] kind of mind, and cannot stand these novelties and subtleties”, as Guicciardini described the Pope. Bellarmine knew what would happen if the Pope found about Galileo’s “incursion into the sacristy,” there would be a show down. That is probably why he was trying keep Galileo away from Rome.
But Galileo was now in Rome and he thought he had “conclusive physical proof” of the Copernican system. It was his theory of tides. Seven years earlier, Kepler in his Astronomia Nova, had proposed an explanation of the tides as an effect of the moon’s attraction, which turned out to be correct. Galileo rejected Kepler’s theory as an astrological superstition, and put forth his own theory that the tides were direct consequence of the earth’s combined motion which caused the sea to move at a different speed from the land. His theory contradicted his own research on terrestrial motion and was a relapse back into Aristotelian physics; the theory predicted that there should be only one high tide a day and that at precisely high noon; this contradicted by what everybody knew that there were two high tides a day and that their occurrence shifted around the clock. The whole theory was such a contradiction to the facts and so absurd as a mechanical theory, it is difficult to explain why he held to it. A possible explanation is that Galileo had not extended his new understanding of terrestrial motion to the motion of the heavenly spheres, where the natural motion of the celestial spheres was circular and uniform. Thus in his tide theory, the tides were the consequence of this celestial motion of the earth. Remember that Galileo accepted the astronomical system of Copernicus in which the planets, and the earth, moved in the circular and uniform motion of the celestial spheres. Armed with his “conclusive physical proof”, Galileo decided to make a direct assault on the Pope. But all his friends, who had direct access to the Pope, Cardinals Dini, Barberini, del Monte, etc., refused to act as intermediaries. Galileo was able to persuade Cardinal Alessandro Orsini, a youth of twenty-two, to approach the Pope on his behalf. The Cardinal approached the Pope in the Consistory and spoke to the Pope on behalf of Galileo. The Pope apparently told the Cardinal to tell Galileo to give up that opinion. Thereupon Orsini said something, urging his cause, and the Pope cut him short and told him he would refer the business to the Holy Office. After Orsini left, the Pope summoned Bellarmine, and, after a brief conversation, they decided that the opinion was erroneous and heretical. On February 23, 1616, four days after they were summoned, the Qualifiers (that is, the theological experts) of the Holy Office met to give their opinion on the two following propositions:
(1) The sun is the center of the world and is wholly immovable of local motion.
(2) The earth is not the center of the world nor immovable, but moves as a whole, also with diurnal motion.
The Qualifiers gave their opinion that the first proposition was “foolish and absurd, philosophically and formally heretical inasmuch as it contradicts the doctrine of the Holy Scripture in many passages, both in their literal meaning and according to the general interpretation of the Fathers and Doctors.” The second proposition was declared “to deserve the like censure in philosophy, and as regards theological truth, to be erroneous in faith.” But the Qualifier’s verdict was overruled, for the time being, under pressure from the Cardinals; and their verdict was only published seventeen years later. Instead of it, on March 5, the General Congregation of the Index issued a more moderate decree, in which the fatal word “heresy” does not appear. The decree says in part:
“Therefore, in order that this opinion may not insinuate itself any further to the prejudice of Catholic truth, the Holy Congregation has decreed the said Nicolaus Copernicus, De revolutionibus orbium, and Diego de Zuniga, On Job, be suspended until they be corrected, but that the book of the Carmelite Father, Paolo Antonio Foscarini, be altogether prohibited and condemned, and that all other works likewise, in which the same is taught, be prohibited, as by this present decree it prohibits, condemns, and suspends them all respectively.”
Copernicus’ book remained on the Index for exactly four year. In 1620 the “corrections” were published and thereafter any Catholic publisher was free to publish the book, although no Catholic or Protestant publisher did so for three hundred years. Not Galileo nor any of his works were even mentioned in this decree. The decree does declare that the doctrines of the motion of the earth and the immobility of the sun to be false and “altogether opposed to the Holy Scriptures.” The decree seems to condemn and prohibit any book or work that teaches these doctrines or any thing taught in the books or works explicitly condemned and prohibited by this decree. This could be interpreted as applying to Galileo’s works, especially the Letter to Castelli and the Letter to the Grand Duchess.
Six days after the decree Galileo was received by the Pope in an audience which lasted three quarters of an hour. While everything was done to spare him public humiliation, he had been confidentially but firmly enjoined to keep within the prescribed limits. This happened between the session of the Qualifiers on February 23 and the publication of the decree on March 5. On Thursday, February 25 there is the following entry in the Inquisition file:
“Thursday, 25 February 1616. The Lord Cardinal Mellini notified the Reverend Fathers, the Assessor, and the Commissary of the Holy Office that the censure passed by the theologians upon the propositions of Galileo – to the effect that the Sun is the center of the world and immovable from its place, and that the Earth moves, and also with a diurnal motion – had been reported; and His Holiness has directed the Lord Cardinal Bellarmine to summon before him the said Galileo and admonish him to abandon the said opinion; and, in case of his refusal to obey, that the Commissary is to enjoin him, before a notary and witnesses, a command to abstain altogether from teaching or defending this opinion and doctrine and even from discussing it; and, if he do not acquiesce therein, that he is to be imprisoned.”
The principal point of controversy concerning the trial of Galileo later in 1633 was on the question whether Galileo refused to obey; if he did refuse, then the procedure outlined would have been followed, that is, was he commanded “to abstain altogether from teaching or defending this opinion and doctrine and even from discussing it”. The evidence seems to be that the command foreseen “in case of his refusal to obey” was not served. He was only “admonished to abandon the opinion he had hitherto held” and he obeyed. The evidence is an entry found among the Decreta of the Congregation in the minutes of the meeting on March 3, 1616, and a certificate which Bellarmine wrote of the proceedings in which Galileo was admonished but not adjured or punished. Bellarmine’s certificate and the minutes of March 3 seem to indicate that Galileo was not under any absolute prohibition from teaching, defending, or even from discussing it.
After the decree of March 5, Galileo stayed in Rome for another three months; the alarmed Duke of Tuscany ordered Galileo back to Florence. And for the next seven years Galileo published nothing. For the next two years he was mostly ill, but did some minor work like making a naval telescope. After two years in 1618, he could not hold back no longer; he sent his treatise on the tides to Archbishop Leopold of Austria hoping that it would be printed in Austria; nothing came of it.
In the same year three comets appeared in the sky, announcing the beginning of the Thirty Years War (1618-1648), which was really a series of wars between Roman Catholic and Protestant countries. These three comets was also the occasion of one of most disastrous of the many controversies in which Galileo became involved. It all started with a lecture, later published, by the Jesuit Father Horatio Grassi of the Collegium Romanum, on the motion of the comets. It proposed that the comets move in regular orbits like the planets, at a distance far greater than the moon’s orbit. To support this view, Grassi quoted with approval Tycho’s conclusions concerning the famous comet of 1577. Grassi’s treatise was another step of Jesuits’ retreat from Aristotle, who had maintained that comets are earthly exhalations in the sublunary sphere, and an indication of the Order’s adoption of Tychonic system to replace the discredited Ptolemaic system. When Galileo read the treatise, he was outraged; it did not even mention his name or his contribution to the theory of comets in his endorsement of Tycho’s views in the Letters on Sunspots. Galileo did not attack Grassi directly, under his own name, but indirectly by signing the name his former student, Mario Guiducci, to his treatise Discourse on Comets; the manuscript, most of which has survived, is in Galileo’s handwriting. Galileo now withdrew his endorsement of Tycho’s views on comets, and now asserts that comets are not real objects at all, but only optical illusions like the aurora-borealis or the mock-suns, caused by the reflection of earthly vapors, which reach up into the sky past the moon. If they were real, they ought to appear larger as they approach the earth and smaller as they recede from the earth and then vanish altogether. Why did Galileo reverse his position? The Tychonic system as compromise between Copernicus and Ptolemy must be rejected, so that the choice would remain Copernicus and Ptolemy. But Galileo had another reason for denying that comets really existed; their paths were very elliptical, and they could not be reconciled with the circular orbits in which all the heavenly bodies must move about the sun. At the end of treatise, Grassi is reproached for not mentioning Galileo’s discoveries and Father Scheiner for “misappropriating the discoveries of others”, that is, his. Since Galileo did not sign his own name, Grassi replied under a transparent anagram “Lothario Sarsi Sigensano” (Horatio Grassi Salonensi). Grassi ignored Guiducci, and attacked Galileo directly with vehemence. He showed that Galileo claimed priority for discoveries which are not his own. He replies to Galileo’s attack on the Tychonic system; he asks, since Ptolemy was refuted and Tycho is rejected by Galileo, does this mean that Grassi should have endorsed Copernicus, which is condemned and abhorred by every good Catholic?
Grassi’s pamphlet was published in 1619 with the title The Astronomical and Philosophical Balance. Galileo answered with his famous Il Saggiatore, The Assayer, who measures things on the finer balance designed for precious metals. It took Galileo two years to write it, and it was published 1623, four years after Grassi’s counter-attack. The Assayer is written in the form of a letter to a friend, Monsignor Cesarini, Chamberlain to the Pope. It begins with a tirade against all those have tried to rob Galileo “of the glory of his discoveries”. Galileo adds to this group Marius von Gunzenhausen, the discoverer of the spiral nebula in Andromeda, which was the first nebula to be observed. In this context Galileo says,
“You cannot help it, Signor Sarsi, that it was granted to me alone to discover all the new phenomena in the sky and nothing to anybody else. This is the truth which neither malice nor envy can suppress.”
The main purpose of The Assayer is to destroy the Tychonic system, by demolishing the reputation of Tycho. He also explains the reason which forced him to break his resolve not to publish any more; Galileo’s enemies, who have unsuccessively tried to steal his discoveries, now try to attribute him “the work of another”, namely Guiducci’s pamphlet. He adamantly denies having any part in the pamphlet, apart from discussing the subject with Guiducci. A major part of the work is a sarcastic attack on everything that Grassi said, regardless whether he had blundered or hit on the truth. Grassi often tried to prove a good point with a bad argument. Galileo found plenty for him to attack. Most of it irrelevant and sophistries. In the midst of this diatribe Galileo made a distinction that became very important for the theory of knowledge: the distinction between primary and secondary qualities. The primary qualities are those qualities that are in things, such as position, number, shape, and the motion of bodies; and secondary qualities are those qualities that exist only in the perception of knowing subject, such as colors, tastes, and odors. This distinction played an important part in British Empiricism, in the philosophies of John Locke (1632-1704) and George Berkeley (1685-1753), and in the formulation of the mechanistic view of the universe.
This controversy had a very important consequence for Galileo. Galileo’s attack on the Jesuit Father Grassi along with the equally unprovoked attack on Scheimer, turned these two influential members of the Jesuit Order into implacable enemies of Galileo. The result of this was that the Jesuit as a body turned against Galileo. Father Grienberger, who succeeded Clavius as head of the Roman College, was to remark later, “if Galileo had not incurred the displeasure of the Company, he could have gone writing freely about the motion of the earth to the end of his days.”