The NOVA documentary, Galileo's Battle for the Heavens, presents the struggle between Galileo and the church for his vision of the cosmos. This drama, the Galileo Affair, has been told and retold. It is the story of a man whose guide was fact and not inherited wisdom. A hero in the battle between faith and reason. In Against Method, Paul Feyerabend also presents Galileo as a heroic figure. For Feyerabend, Galileo's guide was often intuition not fact. Feyerabend believed that great science does not work the way it is painted in textbooks. He used Galileo as an example since Galileo's commitment to Copernicism did not agree with facts known at the time. In other words, Galileo himself was going on faith.
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Much has been written about Galileo's problems with the church over his Dialogue Concerning the Two Chief World Systems. In the Dialogue, Galileo's 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 alternative 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.
Straw man arguments aren't scientific arguments. To make matters worse, Galileo narratives typically provide sketchy discussions of the strengths and weaknesses of the Copernican and Ptolemaic models. In Against Method, Paul Feyerabend spends several chapters discussing Galileo and both the arguments and counter-arguments for Copernicism from a philosophical and scientific point of view. The noted philosopher's conclusions are at odds with the digested version of the controversy presented in the typical biography:
...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).
The problem identified by Feyerabend is only one issue with modern portrayals of the Galileo Affair. Since there are so many Galileo Myths, these portrayals seem to have trouble separating fact from fiction ( see The Galileo Myths). They also often share the same missing pieces:
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.
Stellar parallax was not the only problem with the Copernican Model. Planetary models are mathematical models. They can be used to predict the position of any planet at any time during a year. Deciding on a model should have been as easy as comparing predicted positions with actual positions for each of the different models. But it seemed that all the models (excepting the Keplerian) were observationally equivalent. This has been confirmed by modern computer-aided analyses [_2_] . The Copernican Model used perfect circles when an accurate model required the use of Kepler's ellipses.
Kepler's model was relatively new but it had already achieved important successes even during Galileo's lifetime. Kepler's model predicted that Mercury would pass between the Earth and Sun on November 7,1631. This is known as a Transit of Mercury (see Gassendi's Transit). A Catholic priest, Pierre Gassendi, asked astronomers around Europe to help verify the Transit. The Transit occurred within minutes of Kepler's predictions. Gassendi calculated the error of Kepler's model as 14 minutes (of an arc) while that of the Ptolemaic model was 4 degrees 25 minutes. The Copernican Model was worse than either at 5 degrees (see Nicolaus Copernicus Thorunensis). Galileo ignored this important experiment. He had announced his decision to ignore Kepler's work well before the experiment. (see Galileo's Contemporaries).
Galileo's Battle for the Heavens is all about Galileo's struggle with the Catholic Church over his support for the Copernican Model. Copernicus, himself, never had any similar struggles (see Copernicus Timeline). What happened after Copernicus died says much about what happened during his life. Instead of being buried in a cemetery, like most members of the diocese, he was honoured with a burial inside Frombork Cathedral [_3_] . Copernicus was either in the care or employ of the church from the time he was orphaned at age 10 to his death at age 70. The church funded his university education, and provided him with an income (through sinecures) even while at university. In his last days, he was being cared for by a church canon, at the request of a Catholic bishop. About 10 years before his death Copernicus's ideas reached the Vatican. The result was a letter asking him to share his work with other scholars (see Schonberg's Letter). Copernicus ignored the request. It then fell to Tiedemann Giese, a Roman Catholic bishop and close friend of Copernicus, to convince Copernicus to publish. Copernicus finally agreed, but only to publish his mathematical tables. It was Geise who convinced Copernicus to publish his theory as well. Geise, being one of Copernicus's closest friends, did warn him to expect pushback from other astronomers [_4_] . When the manuscript was finally published, it contained a copy of Schonberg's Letter, the imprimatur of the pope, and an expression of thanks to the pope and Geise.
Kepler is usually credited with our modern view of the solar system. Kepler was not a Catholic. Born a Lutheran, he had been excommunicated from the Lutheran church for some of his beliefs. He remained a devout Christian, but outside of any formal tradition. Nothing seemed to come easy for Kepler. Early in his career, Kepler had trouble borrowing a telescope. Galileo ignored his requests. It would be left to the Catholic bishop of Cologne to lend him one. Over time Kepler developed a close relationship with the Austrian Jesuits (especially Paul Guldin). Kepler would use the Jesuit network of institutions as his private postal service. The Jesuits chased down and returned a manuscript that was stolen from him. Niccolo Zucchi, a master Jesuit telescope builder, built a telescope for Kepler, at Guldin's request. Kepler acknowledged the help with a gushing thank you to the Jesuits in his last book, the Somnium.
Galileo, Kepler and some Jesuits disagreed on the design of telescopes. Galileo's preferred design used a convex objective and a plano-concave eyepiece. A few years after Galileo introduced his telescopes, Kepler proposed a design with a convex objective and a convex eyepiece. This design was largely ignored; except for a group of Jesuits, led by Christopher Scheiner. Scheiner started building and using telescopes using Kepler's design. He detailed this in his work, Rosa Ursina, in 1630. Astronomers remained skeptical. But not for long. Shortly after Galileo's death, astronomers discarded the Galilean design in favour of Kepler's. Scheiner was only one of many church scientists who made important contributions to the early development of telescopes. This included building the first crude reflecting telescope, inventing a telescope mount that is still used widely today and proposing the reflecting telescope design that would dominate in the twentieth century. Fathers of the Telescope details some of the contributions of church scientists to the early development of the telescope.
Narratives such as Galileo's Battle for the Heavens do Galileo a tremendous disservice. Galileo's greatness could be argued using only one of his works, Discourses and Mathematical Demonstrations Relating to Two New Sciences. Yet Galileo narratives unnecessarily embellish his record with myth and hyperbole. As a result, it is difficult to know where the real Galileo ends and where the mythical Galileo begins .
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. Modern astronomical telescopes do not derive from Galileo's design but from Kepler's design (see Myth 5,The Galileo Myths). Galileo was not the first to apply mathematics to nature. This tradition had been established centuries before in Oxford (see The Oxford Calculators) and Paris (the Doctores Parienses) but had spread through Europe (see Myth 6,The Galileo Myths). Several of Galileo's proofs and laws mentioned had been developed centuries before (including the time-squared law, and the geometric proof for the mean speed theorem) by Bishop Oresme. Galileo was not a lone voice for experimentation or a lone voice against Aristotle (see Myth 9,The Galileo Myths). The Tower of Pisa experiment is not a good example of Galileo's belief in experimentation because it never happened (see Myth 1,The Galileo Myths) . Neither was Galileo able to determine the rate of acceleration due to gravity unless you consider a 50% error close enough (see Myth 10, The Galileo Myths) [_5_] . Galileo's contemporaries amongst the Jesuits were the first to derive an accurate estimate of the acceleration due to gravity (see Galileo's Contemporaries). And Galileo was not "remanded to a small room in the Palace of the Inquisition". It was a massive 5-room suite in the Palace that included a room for the personal valet the Inquisition had provided (see Myth 3,The Galileo Myths). The suite was larger than an average American home and had two windows that looked out on the Vatican gardens. To accommodate Galileo's preference for Tuscan cuisine, food and wine was provided for him by the Tuscan embassy. A floor plan of the suite is shown below.
The Galileo Affair has become a symbol for the conflict between church and science. This is curious. Science eventually adopted Kepler's model, not Galileo's favourite, the Copernican. Neither can cosmology be considered a mainstream science. If a symbol is needed, Gregor Mendel seems a better choice (see Gregor Mendel and Evolution). His work is core to any modern understanding of biology, agriculture or medicine. The problems don't go away even if we agree to base everything on early seventeenth century cosmology. Doesn't it make more sense to use the cosmologist from Galileo's time who had the most influence on the future astronomers. That would be Johannes Kepler. The image below is a word cloud (see wordle.net) of references to scientists in Newton's great work,Philosophiæ Naturalis Principia Mathematica.
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 for two prebends for Galileo. Prebends are similar to sinecures, a recurring grant with little 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 concerned that her father may overindulge in 'prison' and thereby endanger his health [_7_] .
The Galileo Affair raises many questions that could be used to bring students a bit closer to the nub of science. What is the difference between a theory and a model? What constitutes 'proof' for a theory? How do you validate a model? Why are actual physical experiments considered the 'gold standard' when trying to prove a theory? Why "being right" is not good enough in science? These are not the questions that are asked by educators in their worksheets for "Galileo's Battle for the Heavens". They can hardly be blamed. Galileo's Battle for the Heavens, like many treatments of the Galileo Affair, do not consider the questions important. Scientists do. It seems that with the Galileo Affair, the story takes center stage and science is demoted to a sideshow.