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Galileo's Battle for the Heavens

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The NOVA documentary, Galileo's Battle for the Heavens, presents the heroic struggle between Galileo and the church for his vision of the cosmos. This drama, the Galileo Affair, is the story of a man guided by facts and reason. In Against Method, Paul Feyerabend also presents Galileo as a heroic figure. For Feyerabend, Galileo's guide was more intuition than facts. Feyerabend believed that great science must sometimes work against the facts. He demonstrated that Galileo's commitment to Copernicism did not agree with facts known at the time. Galileo, a hero in the struggle between faith and reason, was himself going more on faith than reason.

...while the pre-Copernican astronomy was in trouble (was confronted by a series of refuting instances and implausibilities), the Copernican theory was in even greater trouble (was confronted by even more drastic refuting instances and implausibilities).
Paul Feyerabend, Against Method

Galileo's Straw Man

Much has been written about Galileo's problems with the church over his Dialogue Concerning the Two Chief World Systems. In the Dialogue, Galileo argued for the Copernican Model against the Ptolemaic Model. This was Galileo's straw man argument. In a straw man argument, you create or choose an opposing argument that is easy to defeat, then proceed to destroy it. Your own argument wins by default. The problem with Galileo's argument was that there were at least 5 "world systems"! When Galileo wrote his Dialogue, the Ptolemaic model had been already supplanted by other models [_1_] .

The 5 major planetary models that were in play when Galileo published the Dialogue were the Tychonic, Ursine, Capellan, Copernican and Keplerian. Three were geo-heliocentric (Tychonic, Capellan, Ursine) where some bodies circled the sun and some the earth. Two were heliocentric (Copernican and Keplerian). Early on, Galileo's Battle for the Heavens describes Galileo's discovery that Venus went through phases. This could only be explained if Venus was orbiting the Sun and not earth. If the choice was between a Copernican model (sun-centred) and Galileo's straw man (the earth-centred Ptolemaic) it was clear proof for the Copernican Model. But it wasn't a two-way choice. All five models mentioned were compatible with the Galileo's discovery. Galileo's Battle for the Heavens, like most discussions of the Galileo Affair, has fallen prey to Galileo's Straw Man. The program never mentions any models except for the Copernican and the Ptolemaic.

The Galileo Affair-The Elephants in the Room

Galileo's contemporary, Johannes Kepler, was never mentioned once during the entire duration of Galileo's Battle for the Heavens. This wouldn't happen if the discussion was really about science. Like other discussions of the Galileo Affair, it is more about the clash between science and the church than science or history. That makes several scientific and historical facts "awkward". Kepler is only one of four elephants in the room that are commonly avoided:

  • Johannes Kepler
  • Copernicus
  • Stellar Parallax
  • Ephemerides

Kepler is awkward for Galileo narratives for several reasons. If Kepler's planetary model was largely correct, why did Galileo ignore him? Galileo had decided to ignore everything that Kepler did or wrote because he did not want to seek out "the nuggets of real gold in Kepler's heap of dross" [_2_] . This means that he ignored his 3 laws of planetary motion, his belief that the tides were caused by the moon, and his suggested design for refracting telescopes. Kepler's design of telescope, which used convex lenses for both the eyepiece and objective, would replace Galileo's design within a decade of Galileo's death.

If Galileo's interactions with the church are important shouldn't Kepler's interactions be also. Kepler's most loyal supporters were Jesuit priests from Austria. And Kepler wasn't even Catholic, he was an excommunicate Lutheran. Kepler used the network of Jesuit institutions as his private postal service. The Jesuits were the first champions of Kepler's refracting telescope design (see Jesuits and the Early Telescope). They had their master telescope maker, Niccolo Zucchi, build him a telescope. They even chased down and returned a manuscript that had been stolen from Kepler. Kepler used the appendix of his last book, the Somnium, to thank them for their loyalty. Outside of the Jesuits, it was a French Catholic priest who arranged an international experiment that became the first important support for Kepler's planetary model (see Gassendi's Transit).

Galileo was wrong to ignore Kepler. His successors did not repeat his mistake. The image below is a word cloud (see wordle.net) of references to scientists in Newton's great work,Philosophiæ Naturalis Principia Mathematica .

Word Cloud - Newton Principia

While Copernicus is not ignored in Galileo narratives, his relations with the church are. Copernicus was orphaned at about the age of 10. From that time until his death he was either in the employ or care of the church. The church paid for his education at some of the best universities in Europe, and gave him the position of canon at a Polish diocese after graduation. The church and local nobility sought his advice in diplomacy, finance, medicine, military defence and astronomy. When the Vatican found out about his new model of planetary motion, it sent him a letter asking him to share his work with others, and offered to pay for its publication (see Schonberg's Letter). It was a German professor (Rheticus) and a Polish bishop (Tiedeman Geise) that finally convinced Copernicus to publish. When Copernicus opted to only publish his tables it was Bishop Giese who convinced him to publish the explanation as well [_3_] . Copernicus fell ill before the publication of his work and was cared for by a canon of the church at the urging of another Catholic bishop (Danticus). Copernicus' was buried inside a cathedral, near the altar he had tended during his life [_4_] . A timeline of Copernicus's life is here.

The Copernican model featured a moving earth with the sun being stationary. There are necessary consequences of a moving earth. One is stellar parallax (see Copernicus and Stellar Parallax). If the earth was moving relative to the sun it demands that viewers on earth be able to see some change in the relative positions of nearer and distant stars over the course of a year. No-one in Galileo's time was able to detect any change in the positions of the different stars. Stellar parallax was eventually detected, but not until 1838.

If you compare the predictions of the various cosmological models (excepting the Keplerian) and compare them to a record of astronomical observations (an ephemeris) you will find they perform about the same. This has been confirmed by modern computer-aided analyses [_5_] . Galileo, his contemporaries and even Copernicus knew that the Copernican Model did not seem to fit the data any better than its competing models. The Copernican Model used perfect circles when an accurate model required the use of Kepler's ellipses.

Galileo and the Church

Galileo's own problems with the church over the Copernican Model are well-known. He was eventually placed under house arrest in a large summer villa, Il Gioello, that Galileo had been renting from one of the richest banking families in Florence (the Martellinis). "House arrest" didn't mean quite the same thing to the Roman Inquisition as it does today. It was most often a restriction of movement. If the sentence really involved a house arrest, there would have been no need to specify that he shouldn't cross the Arno, which was about 2 kilometers from his villa. At the time Galileo was 69. Until that time, Galileo had enjoyed the favour of the church. This included monetary support for his research. When Pope Urban VIII was elected pope, he arranged two prebends for Galileo. Prebends are recurring grants with few associated responsibilities [_6_] . Galileo did have disputes with several Jesuits but for the most part these were scientific disputes, as happen even today. Throughout his life he remained close to many Roman Catholic clergy. Two priests, Pierre Gassendi and Marin Mersenne, could be considered Galileo's ambassadors outside of Italy. One of his 'prisons' during his trial was the palace of one of his best friends, Archbishop Piccolomini of Siena. Although the Inquisition considered his stay there as a "formal prison", few others would. Throughout his stay, he was wined and dined by his friend. In fact Galileo's daughter was very concerned that her father may overindulge in 'prison' and thereby endanger his health [_7_] .

The Galileo Affair happened when Galileo was already 69 years old. Until that time, Galileo had enjoyed the favour of the church. The Pope had arranged two prebends for Galileo. Prebends are similar to a recurring grant [_8_] . His close friends included Archbishops and Cardinals in the Inquisition. He had many other friends who were simple clergy. Early on, his relations with the Jesuits was very good. The Jesuits of the Collegio Romano had arranged a special dinner for him Becelebrating his early telescope discoveries. This relationship soured over time. Galileo was quick to accuse others of plagiarism. He had unjustly accused Christopher Scheiner and Orazio Grassi, both Jesuits, of plagiarism. This is a terrible accusation for an academic.

Galileo's own problems with the church over the Copernican Model are well-known. He was eventually placed under house arrest in a large summer villa, Il Gioello, that Galileo had been renting from one of the richest banking families in Florence (the Martellinis). "House arrest" didn't mean quite the same thing to the Roman Inquisition as it does today. It was most often a restriction of movement. If the sentence really involved a house arrest, there would have been no need to specify that he shouldn't cross the Arno, which was about 2 kilometers from his villa. Galileo did have disputes with several Jesuits but for the most part these were scientific disputes, as happen even today. Throughout his life he remained close to many Roman Catholic clergy. Two priests, Pierre Gassendi and Marin Mersenne, could be considered Galileo's ambassadors outside of Italy. One of his 'prisons' during his trial was the palace of one of his best friends, Archbishop Piccolomini of Siena. Although the Inquisition considered his stay there as a "formal prison", few others would. Throughout his stay, he was wined and dined by his friend. In fact Galileo's daughter was very concerned that her father may overindulge in 'prison' and thereby endanger his health [_9_] .

The Galileo Myths

Sadly, Galileo's Battle for the Heavens and its associated website repeats several of the most common Galileo myths (see The Galileo Myths). This from an award-winning documentary that is used widely in science education. For example, Galileo was not "remanded to a small room in the Palace of the Inquisition". It was a large 5-room suite that came with a personal valet and room service that included the finest of Tuscan food (see Myth 3 of Galileo Myths). A floor plan of the suite is shown below. Other myths in the program or learning materials include Myth 1, Myth 5, Myth 6, Myth 9, Myth 10, Myth 16, Myth 21 and Myth 22 from the Galileo Myths page.

Galileo's Vatican Suite

A Hollow Victory

By the end of Galileo's Battle for the Heavens, the program had successfully built and destroyed a straw man and had successfully navigated around all the elephants in the room in the Galileo Affair. It is a hollow victory. In the process it missed the most important scientific issues. That is because the program, like many discussions of the Galileo Affair, was not about science (see Modern Science). This is signalled by the program's own byline: "Witness Galileo's famous struggle to persuade church authorities of the truth behind his discoveries about the cosmos". Persuading people of the truth is the stuff of debating clubs not scientists. Being right is not good enough in science. 'How' you are right matters. Your proofs must be valid. This is as true today as it was 400 years ago (see Wegener and Galileo).


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Copyright Joseph Sant (2019).
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1. Michael Hoskin, Cambridge University Press 1999, Cambridge Concise History of Astronomy, , 117
By the time the Dialogue had been published most of those believing in an earth-centered system had adopted one of the geo-heliocentric systems.
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2. Max Caspar, Courier Dover Publications 1993, Kepler, , 137
Caspar refers to this quote from an article by Rosen in the footnotes of his discussion as to why Galileo may have chosen to ignore Kepler through the last three decades of his life.
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3. Repcheck, Jack, Simon and Schuster,, Copernicus' Secret: How the Scientific Revolution Began, , p.147-148
Repcheck quotes Rheticus's own words in crediting Giese in convincing Copernicus to publish. The book also discusses Copernicus's own argument for NOT publishing his theory.
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4. Goddu, Andre, Brill Academic Publishers, Copernicus and the Aristotelian Tradition, , p. 436
Based on custom, Copernicus should have been buried near the altar he was responsible for, the altar of Saint Vaclav. On exhuming bodies near the altar, a corpse matching the age of Copernicus was found, and the DNA of this corpse matched that of a hair found in one of Copernicus's books.
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5. Babb, Stanley E.,, Isis, Sept. 1977, Accuracy of Planetary Theories, Particularly for Mars,, , pp. 426-34
In this article Stanley Babb compares the predictions of the Copernican and Ptolemaic models against the actual planetary positions using computer-based statistical analysis. The results did not show a dramatic difference between the two systems, but the earth-centred system (the Ptolemaic) did perform better for planets such as Mars.
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6. Rowland,Wade, Arcade Publishing, Galileo's Mistake, , 57
Galileo was the beneficiary of two prebends from the diocese of Pisa and the diocese of Brescia. Typically prebends provide a right to a share of the revenue of a diocese or parish in return for some associated responsibilities. But there were no responsibilities. Not even to ever show up in either Pisa or Brescia. It is reasonable to interpret the prebends as ongoing (research) grants which Galileo could spend as he pleased. There is no indication that these prebends were ever revoked even after his trial.
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7. Sobel, Dava., Bloomsbury Publishing USA, 1999., Galileo's daughter: A historical memoir of science, faith and love., , pp. 279
This is a collection of letters from one of Galileo's daughters to him while he was in Rome and Siena. She expressed her concern about his habit of overindulging.
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8. Rowland,Wade, Arcade Publishing, Galileo's Mistake, , 57
Galileo was the beneficiary of two prebends from the diocese of Pisa and the diocese of Brescia. Typically prebends provide a right to a share of the revenue of a diocese or parish in return for some associated responsibilities. But there were no responsibilities. Not even to ever show up in either Pisa or Brescia. It is reasonable to interpret the prebends as ongoing (research) grants which Galileo could spend as he pleased. There is no indication that these prebends were ever revoked even after his trial.
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9. Sobel, Dava., Bloomsbury Publishing USA, 1999., Galileo's daughter: A historical memoir of science, faith and love., , pp. 279
This is a collection of letters from one of Galileo's daughters to him while he was in Rome and Siena. She expressed her concern about his habit of overindulging.
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