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At home at Bellosguardo Galileo followed events in Rome. But he did this second hand, via his correspondents and did not entirely register the change of atmosphere that was slowly taking place. In addition he was frequently ill, or concerned with family matters.

His brother Michelangelo, who was still a musician in Germany, sent his entire family - wife, eight children and nursery maid - away from poverty and war, and home to Galileo and the security of Tuscany. They lived at Bellosguardo for a good year and filled the house with more life than Galileo really appreciated.

Then there were his daughters in the convent of San Matteo. They needed constant visits and help when they wanted contact with the outside world. A ceaseless stream of small gifts passed between father and daughters - and when Galileo was absent from Florence, they kept in contact by letter.

His boy Vincenzio was still a worry. When Pope Urban finally found a sinecure for Galileo's son, he immediately turned it down because he did not want to accept any support from ecclesiastical quarters.

Taken as a whole the reports he was getting from Rome were still quite optimistic in tone. Above all the Lynceans had maintained their influence at the papal court. Prince Cesi was highly respected, and Ciampoli was still the Pope's Secretary. He could confirm that Galileo personally enjoyed His Holiness' high regard. Father Grassi's attack on The Assayer, with its ominous hint that Galileo's view of natural philosophy was incompatible with the Catholic understanding of the Eucharist, was finally printed in 1626. The attack was probably of little consequence (but see postscript p. 204). Grassi's book was published in Paris, probably on grounds of discretion because The Assayer was, after all, dedicated to the Pope. Anyway, Galileo did not much concern himself with Grassi's answer - he regarded the comet debate as at an end.

Despite his problems, Galileo now decided to risk setting out his theory, and hazarding everything on the tides. He wanted to write the great, definitive work that no one would be able to surpass; a unified account in classical dialogue form, in Italian, just as his father half a century before had written his great work Dialogue on Ancient and Modern Music. It was precisely the "ancient and modern" that Galileo also wanted to discuss: the Ptolemaic system versus the Copernican. Within the dialogue the certain arguments in favour of Copernicus would be advanced, accompanied naturally by the reservations necessitated by the Church's attitude. Galileo believed he had Pope Urban's permission for such a "contingent" discussion.

But he was working alone at Bellosguardo. His contact with others was limited largely to discussions and correspondence with people who agreed with him. Galileo had no great patience with those who refused see that Copernicus was right, and his patience did not increase as he wrote his way through the Copernican arguments. As the work progressed, his reservations and provisos became fewer and more brief - the reservations that were to show that he "only" regarded the idea of the Earth's motion as hypothetical speculation.

Galileo had long known what he would call his great work. Its title was to be Discourse on the Ebb and Flow of the Sea (Dialogo delflusso e deflusso della marea).

The writing progressed slowly and with long pauses. His family demanded their share of his attention the whole time. However, they were not only a source of problems: Vincenzio had at last finished his studies at Pisa, and had come home to Florence with a degree in law. Immediately after this he got engaged and was married in January 1629. Galileo's first grandchild was born in December of that same year and was named after him.

The university of Pisa wanted to get Galileo off its payroll, as his employment there was a pure formality and meant little more than that the university had to pay his salary. Galileo mobilised the young Grand Duke, who eventually saw to it that the contract that his father Cosimo II had drawn up, was respected. But such things took time and energy.

On Christmas Eve 1629 - after an intensive period of work - he wrote to Prince Cesi mentioning a new, serious health problem: Galileo the observer, the telescope virtuoso, the mathematician with the eyes of the lynx, was slowly losing his sight.

But his greatest difficulties lay in the actual realisation of his project. He came across a good many problems which he had to reconsider, especially in connection with tides, which without doubt were difficult to solve. The dialogues were also to elucidate various phenomena connected with motion, so it was necessary to go through all the old material he had, right back to his time at Padua. Furthermore, these observations often produced interesting digressions which were highly suited to the dialogue form and imparted life to his account. But it took time to put it all into words.

While the work on the tides and their significance slowly took shape under Galileo's pen in Florence, work was also going forward in Rome. The German Jesuit, Father Scheiner, wished to publish his meticulous observations of sunspots, but he was also very keen to get in some good swipes at Galileo.

Scheiner's feelings about Galileo are reminiscent of spurned love, which turns to a kind of hate. He had tried to establish an intellectual dialogue with his Mathematical Discourses, but had caught Galileo on what was perhaps his most sensitive spot, the prestige associated with priority of discovery After that, Scheiner was the recipient of Galileo's contempt - or at least that was the way he viewed it himself.

Scheiner's work was a massive volume of 784 double column pages. The "First Book" filled the introductory 66 pages, and was largely a sustained attack on Galileo. Scheiner asserted his right as the original discoverer of sunspots, prior to Galileo and quite independently of him.

And the Jesuit astronomer did not stop there. He maintained that Galileo had not even noticed that the spots described curved trajectories above the Sun's surface, and that he had not actually discovered that the spots were surface phenomena and that the Sun turned on its own axis. If Galileo had ever written anything like this, it was nothing but sheer luck and guesswork!

The movement of the spots was a very important matter, and Scheiner knew it. As a Jesuit he could not openly discuss just how important it was. But he used the remainder of his work to describe this and other solar phenomena in precise detail. Furthermore he sharply criticised the traditional Aristotelian background to astronomy, especially the doctrine concerning the heavens' immutability. This was an attempt to liberate Jesuit science from the straightjacket of Aristotle - but he was unable to follow this up by throwing off Ptolemy's at the same time.

Scheiner's book was called Rosa Ursina. The title was a tribute to his patrons, the Orsini brothers. Prince Paolo Orsini, brother of Cardinal Alle-sandro, had even taken care of the printing, without presumably having read the manuscript with its hefty attacks on Galileo. In any event, the Grand Duke's mathematician received an apology when he wrote a letter of complaint to the Prince.

Galileo probably read the entire book, despite the attacks on him at the beginning, as he had good use for its precise descriptions of sunspots' movements in his own book, which was now nearing completion.

On 1 May 1630 Galileo went to Rome for the fifth time in his life. As usual he stayed at the Ambassador's residence, the Villa Medici. He had with him the manuscript of Discourse on the Ebb and Flow of the Sea. The book was to be printed by the Lyncean Academy, but it was necessary for the author himself to take part in the process leading to the Church's approval - for everyone realised that Galileo's ebb and flow swept across dangerous and muddy waters.

Not only was it quite apparent that he had many powerful enemies in Rome, but he also had to keep to the strict prohibition of 1616: "that the Sun is the centre of the world" was foolish and heretical, "that the Earth moves according to the whole of itself, also with a diurnal motion" was poor philosophy and incorrect creed. It could not be denied that Galileo's voluminous manuscript dealt for the most part with exactly these two subjects.

The solution was to present them as hypotheses, devices, calculational examples.

Galileo had only one audience with Urban VIII this time, but their meeting was pleasant enough, even though the Pope repeated his favourite thesis that all theories were in principle unprovable in the light of God's omnipotence.

The Pope did however distance himself discreetly from the decree of 1616. At least, that was the impression given to a man who had discussed the problem with him in March, a character who now, improbably enough, found himself in Rome and close to the papal court: Tommaso Campanella. That rebellious Dominican had been freed from gaol in Naples in 1626, on the initiative of Urban himself. He was first handed over to the Holy Office in Rome, but in 1629 he gained his complete freedom.

As previously, Campanella wanted open discussion on all cosmological points of view, and referred in a letter to a private comment by Urban VIII to the effect that, if it had been up to him in 1616, there would have been no injunction. In the meantime Galileo - to the enthusiastic monk's bitter disappointment - continued to keep his distance from his ardent admirer, even though Campanella had been partially rehabilitated.

The papal censor in Rome bore the impressive honorary title of "Master of the Sacred Palace". His name was Father Riccardi, and he now had the responsibility of reading and then potentially approving Galileo's manuscript. Father Riccardi came from Florence and was a relative of the Tuscan Ambassador's wife. He had earlier read The Assayer with great pleasure. Riccardi also knew, of course, that the Pope looked kindly on the Grand Duke's mathematician, and had done so for many years.

But even though Riccardi was positive to begin with, his doubts grew as he read. The Discourse on the Ebb and Flow of the Sea promulgated the teachings of Copernicus with great fervour, persuasive force - and stinging irony directed at those who remained stuck fast in Aristotle and Ptolemy. Certainly, it ended by stating that nothing was certain and that Copernicus' doctrine should only be regarded as a hypothesis, but this conclusion seemed to be an unconvincing afterthought to say the least.

Father Riccardi could not take responsibility for it in its present form. He insisted on a new introduction, a clearer summary and the correction of various minor points. The main thing was that the condemnation of Copernicus' book by the Congregation of the Index should not be made to appear ludicrous, but rather as a sensible decision.

Riccardi asked one of the monks, who was a mathematician, to look through the manuscript and make corrections. But the mathematician did not find much to correct. He realised, privately, that Galileo was right, and looked forward to a new discussion on what was acceptable cosmology.

This was not a lot of help to Father Riccardi. He was under pressure from Galileo's influential friends, and grudgingly agreed to give the book provisional approval, on condition that Galileo himself went through the manuscript again and sent the corrected pages to him as they were finished. This enabled the laborious work of typesetting and printing to begin.

For safety's sake - and this shows just how important the matter was - he took the question up with Pope Urban directly. The Pope was satisfied with Riccardi's explanation and gave the go-ahead, but he had one reservation: the title.

Discourse on the Ebb and Flow of the Sea sounded very innocent. But one thing Urban VIII was quite certainly aware of - not least because of their many conversations - was that Galileo did not view the tide as an argument that could be marshalled in favour of a Copernican hypothesis, but as an irrefutable, physical proof.

Papal intervention saved Galileo from the historical ignominy of his magnum opus bearing for all posterity a title that testified to his gravest error. What he thought about the matter is unknown. Urban suggested instead Dialogo sopra i due massimi sistemi del mondo or something in that vein.

Dialogue Concerning the Two Chief World Systems. On 26 June 1630 Galileo travelled home from Rome with a new title for his work, convinced that everything was now in order. He only had to go through it once again, clear up any minor problems with the censor, and maybe add something of importance on the movement of sunspots. After that he would send it back to Rome, where Prince Cesi would take care of the printing on behalf of the

Accademia dei Lincei.

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