The Nova documentary, Galileo's Battle for the Heavens, presents the story of a heroic Galileo battling for truth. This Galileo was a man whose guide was fact and experiment and not inherited wisdom. But the Nova documentary might be more of a story than a true history. In Against Method, Paul Feyerabend also presents Galileo as a heroic figure. But for Feyerabend, H Galileo's guide was often intuition not fact. Feyerabend believed that great science does not work the way it is painted in textbooks, and one support for this was that Galileo's commitment to Copernicism did not agree with facts known at the time.
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Galileo's Battle for the Heavens follows a formula common to many Galileo biographies. Very dramatic, very entertaining, and very sketchy on its treatment of science. Galileo wasn't being driven purely by logic and his critics weren't driven purely by orthodoxy. There is a reason that at least 6 different planetary models were being argued during Galileo's day. All had their strengths. All had their flaws. This is why Galileo should not be faulted for refusing to accept Kepler's Laws of Planetary Motion. Even with Pierre Gassendi's famous experiment in support of Kepler(see Gassendi's Transit ) there was yet little factual support for Kepler's elliptical orbits. Likewise, there were good reasons to hold to the Tychonic or Capellan model over the Copernican model. This is lost to viewers since Kepler and Tycho Brahe are never mentioned in the documentary..
Early on, the program 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 the Ptolemaic (earth-centred) it was clear proof for the Copernican Model. But it wasn't a two-way choice. There was still the Tychonic, Capellan and Keplerian systems. Brahe's system was based on the best set of planetary observations up to that time. The Tychonic system was a geo-heliocentric system where some bodies circled the sun and some the earth. Because of the unusual configuration it meant that Galileo's most famous proof for the Copernican system was consistent with Tycho's system (and the Capellan). Once again, this is lost to viewers because Tycho is never mentioned. Tycho's system was unusual. There had to be reasons that motivated his model. One motivation was that there were troubling theoretical problems with the concept of a moving earth.
There are necessary consequences of a moving earth. One of these would be the observation of 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.
The Copernican Model had an even bigger problem than stellar parallax. It is easy to forget that the Copernican Model was a model. Planetary models can be used to predict the position of planets. Even with the combined genius of Galileo and Copernicus it did not seem that the Copernican model could be tweaked to perform any better than the oldest of the models then being used. Centuries later a computer analysis of the performance of the Copernican Model against the Ptolemaic model would show little significant statistical difference between the two [_1_] . This is because Copernicus and Galileo were tied to using perfect circles, and the problem required the use of Kepler's ellipses.
Many treatments of Galileo's troubles over Copernicism reduce to a simple battle of church against science. Serious treatments of the controversy are not nearly as simple. 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).
Galileo's Battle for the the Heavens only ever mentions two models; the Copernican and Ptolemaic. Which models were the church scientists supporting? There were prominent church supporters of the Tychonic (Christopher Scheiner), the Copernican (Pierre Gassendi) and the Keplerian (Austrian Jesuits). There was probably a Jesuit or Jesuits somewhere in Europe that supported each of the models being argued. The Tychonic was the most popular. The Ptolemaic was already a thing of the past. Gassendi's support of the Copernican model was interesting. If the documentary is to believed, the Inquisition banned Copernicus's work after an inquiry in 1616. Certainly a problem for a Catholic priest. In fact, the inquiry had found that only nine sentences in a 405-page book needed revision (see Copernicus Revisions). Perhaps even more odd than Gassendi's support for Copernicism was the Jesuits support for Kepler.
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. Kepler was an important astronomer of the time even though Galileo biographies rarely mention him. A measure of Kepler's and Brahe's importance is Newton's high regard for their work. The image below is a word cloud (see wordle.net) of references to scientists in Newton's great work,Philosophiæ Naturalis Principia Mathematica. In spite of his importance, nothing seemed to come easy for Kepler. After Galileo introduced the use of telescopes in astronomy, Kepler could not gain access to a telescope. Galileo ignored his request to borrow one. It would be the local Catholic bishop that would come to his rescue by lending him his own. Over time Kepler developed a very special and long-lasting relationship with the Austrian Jesuits (especially Paul Guldin). Kepler would use the Jesuit network of institutions as a surrogate 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.
There is another triangle between Galileo, Kepler and the Jesuits that is often ignored. It was a dispute over 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. Within twenty years, however, astronomers had made a complete about face, discarding the Galilean design in favour of Kepler's design. The advantages of the Keplerian design had become obvious. Scheiner was only one of many church scientists who made important contributions to the early development of telescopes. One of Galileo's contemporaries, Father Marin Mersenne, proposed a design of a reflecting telescope that is still in use today. This was thirty years before Newton 'invented' the reflecting telescope. Another contemporary, the Jesuit Niccolo Zucchi, is commonly credited with building the first crude reflecting telescope. Fathers of the Telescope details some of the contributions of church scientists to the early development of the telescope.
Galileo's Battle for the Heavens is not about science. The program's treatment of the background science was just too weak. But a scientific study was not the writer's intent. Early in the documentary we are warned that what we were about to see was another example of the "recurring clash between religion and science". But if the "science" part of the program is weakened because of what is left out, so is the "recurring clash" part. The program presented Galileo's problems with the church over the Copernican Model as part of a recurring clash. As part of a recurring clash, doesn't it make sense to at least mention what problems Copernicus had with the church over his model.
The documentary wouldn't have had to spend much time on Copernicus's problems with the church over his model. There were none. Copernicus published his major works on the Copernican Model very late in life but his ideas were floating around academic circles in Europe well before that. About 10 years before his death, they reached the Vatican. The only reaction from senior members present then was to send him a letter asking him to share his work with other scholars and arranging for someone to make a copy of his work(see Schonberg's Letter). A key figure in the final publication of his work was Tiedemann Giese, a local bishop. Due to his long service to the church, Copernicus was buried in a privileged location in the local Cathedral after his death.
During Copernicus's time there were two methods that the Vatican could use to support academic research outside of a university or monastery. One was a sinecure. This is effectively "money for nothing"; a regular stipend given to an individual with no associated responsibilities. Another was a prebend. Prebends were used much like sinecures, even though historically they had some associated responsibilities. Early in his career, Copernicus was given three different sinecures. What is little known is that about 100 years later the church would use two different prebends in support of Galileo's research.
Galileo's Battle for the Heavens is an exciting story. But it is a story. A story where Tycho Brahe and Johannes Kepler had never been born. Neither had any of Galileo's important contemporary scientists (see Galileo's Contemporaries). A story where the critical problems with the Copernican model need no mention. A story where Galileo had been confined to "a single room" in the Vatican, instead of a five-room suite overlooking the Vatican gardens [_2_] . A story where requiring nine sentences of a book to be revised is equivalent to a book-ban. Like many great stories, it blurs the line between fiction and reality.