Galileo, the Church and Heliocentricity: A Rough Guide.

A couple of days ago on Twitter, Brian Cox asked the Twitter historians, “Did Galileo know that he would annoy the Church when he published The Starry Messenger?” The very simple answer to this question is, no but a lengthy discussion of the situation developed on Twitter. It was suggested that somebody should produce a short temperate answer to the question as a reference source and after some hesitation I have acquiesced. This will be a relative short presentation of the various stages of this historical process with a minimum of explanation and justification, as Joe Friday used to say, “the facts ma’am, just the facts!” This is of course my interpretation but it is based on a fairly good knowledge of the most recent principal secondary literature on the subject and it is one that I think would find fairly general agreement amongst those who have seriously studied the subject. Those who disagree are welcome, as always, to air their views in the comments but I expect those who choose to do so to base those views on historical facts and not on prejudice.

The first thing to make clear is the situation in terms of astronomy, cosmology and the Church in the first decade of the seventeenth-century before Galileo, Marius, Harriot, Lembo and others changed our view of the cosmos forever with the recently invented telescope. Astronomy and cosmology were not very high up on the Church’s agenda between 1600 and 1610. The vast majority of people, including the experts, still believed in a geocentric cosmos in the form developed by Ptolemaeus, the most modern version being basically that of Peuerbach and Regiomontanus. A very small handful believed in the Copernican heliocentric model, and believed is the right word because it lacked any real form of empirical proof and was burdened by all the physical problems engendered by a moving earth. A probably equally small number favoured a Tychonic geo-heliocentric model with or without a rotating earth and another small number were finding favour with Gilbert’s geocentric model with a rotating earth. All of the discussions were very academic and nothing that could or would threaten the dominance of a solid Bible conform geocentricity, so nothing for the Church to get its knickers in a twist about.

The telescopic discoveries were brand new empirical evidence and the biggest shake up in astronomy since mankind first cast its little beady eyes on the heavens. When he started to make his discoveries, late in 1609, Galileo was very much aware of the fact that he was sitting on the Renaissance equivalent of a Nobel prize, a knighthood and the keys to the treasure chest all in one and also very aware that he almost certainly wasn’t the only person making or about to make these discoveries. In the last point he was of course completely right, Harriot was ahead of him and Marius was breathing down his neck. Galileo was fully aware that if his wished to cash in then he had to get his priority claim in tout suite.

To understand this one needs to look at Galileo’s situation. In 1610 he was a forty-six year old professor of mathematics, stuck in the same rather lowly position for the last eighteen years. He was on the down hill slope to ill health, death and anonymity. He had already done his ground-breaking work on dynamics but hadn’t published it. If he were to die tomorrow nobody would remember him beyond a few close friends and his family. Now he had hit the jackpot and needed to cash in fast. He bunged his principal discoveries together in book form, in what was more a press release than a scientific report, the Sidereus Nuncius, and had it printed and published as fast as possible.

The last thing the Galileo wanted to do at this point was to annoy anybody; he wanted fame and fortune not infamy. He spent as much effort on getting permission to dedicate his small book to Cosimo Medici, the ruler of the Duchy of Florence, his home province, and his sometime private pupil, as he did on his telescopic observations. He also made very sure that the Medici would approve of the name he gave to the newly discovered moons of Jupiter; he was after preferment, which he got as a result of his clever tactical manoeuvring. He would have been mortified if his publication had caused problems with the Church in Rome because that would almost certainly have cost him any chance of an appointment to the Medici court, his main aim at the time. The Medici did in fact drop him when he finally collided with the Church in the 1620s.

The telescopic discoveries, which Galileo was the first to publish, shook up the whole of Europe and not just the Catholic Church. However the contents of Sidereus Nuncius neither disproved Ptolemaeus/Peuerbach nor did they prove Copernicus, as I’ve already explained here. Of course at first they did nothing at all because like all new scientific discoveries they needed to be confirmed by other astronomers. This proved to be somewhat difficult, as the available telescopes were very poor quality and Galileo was an exceptional telescopic observer. In the end it was the Church’s own official astronomers, the members of Clavius’ mathematical research group at the Collegio Romano, who with the active assistance of Galileo delivered the necessary confirmation of all of Galileo’s discoveries.

Hailed now as the greatest astronomer in Europe Galileo travelled in triumph to Rome where he was feted by the mathematicians of the Collegio Romano, who threw a banquet in his honour, had an audience with the Pope and was appointed a member of the Accademia dei Lincei who also threw a banquet in his honour. No signs of annoyance here. Galileo was appointed philosophicus and mathematicus to the Medici court in Florence, as well as professor for mathematics without teaching obligations at the University in Pisa. The humble insignificant mathematician had become a renowned social figure, almost overnight, feted and praised throughout Europe. High Church officials flocked to make his acquaintance and win his friendship, one of these, the Cardinal Maffeo Barberini, became a close friend and the cause of Galileo’s downfall later in his life.

Although nothing in the Sidereus Nuncius disproved the geocentric model of Ptolemaeus the discovery of the phases of Venus a short time later, by Galileo, Lembo, Harriot and Marius, did. The basic geocentric model was dead in the water and the Church had a problem because Holy Scripture clearly implied a geocentric cosmos. Riding on the wave of his fame Galileo wanted to go for the big one. He wanted to go down in history as the man who proved that the cosmos was heliocentric. Unfortunately he lacked a genuine proof. He had evidence that the cosmos was not geocentric and not homocentric but all the available empirical evidence satisfied both a heliocentric cosmos and a geo-heliocentric Tychonic one and it was the latter that most astronomers, still worried about the physical problems of a moving earth, tended to favour.

Around 1613, despite his lack of genuine proof Galileo began to canvas his newly won influential friends in Rome in an attempt to convince them to give their support to a call for the acceptance of a heliocentric cosmos, a dangerous move. The Church was a vast structure set in its ways and like a large ocean liner getting it to stop in full motion and reverse its direction was something that required a lot of time and space, Galileo eager to make his mark in history lacked the necessary patience to wait for the Church to accept the inevitable and was trying to force the pace. Several of his friends including Maffeo Barbarini advised him to calm down and not to force the Church into a corner, but Galileo, his ego inflated by his recent successes failed to heed this sound advice.

In the next couple of years both Galileo and the Carmelite father Paolo Antonio Foscarini tried to tell the Church how to reinterpret those passages of the Bible that contradict a heliocentric interpretation of the cosmos. This was a fundamental failure and guaranteed to annoy the Church extremely, which it did. One should remember that all of this was taking place in the middle of the Counter Reformation and on the eve of the Thirty Years War, which would kill off between one third and two thirds of the entire population of Middle Europe in what was basically an argument about who had the right to interpret the Bible. The Church set up a commission to investigate Foscarini’s book on the subject and the commission came down very hard on heliocentricity, calling it both philosophically (read scientifically) absurd and heretical. The accusation of heresy was not confirmed by the Pope and so was never official Church doctrine, but the damage was done. Cardinal Roberto Bellarmino was instructed to inform Galileo of the commission’s judgement. In a friendly chat Bellarmino did just this, informing Galileo that he could neither hold nor teach the theory that the cosmos was heliocentric. It is important to note that the theory was banned not the hypothesis. One could continue to discuss a hypothetical heliocentric cosmos, one could not, however, claim it to be fact. As many people have pointed out over the centuries this restriction was actually in line with the known empirical facts. The books of Kepler and other Protestants claiming that the cosmos was heliocentric were placed on the Index and Copernicus’ De revolutionibus was placed on the Index until corrected. Interestingly the Inquisition did just that. They removed the handful of passages from De revolutionibus that claimed the heliocentric cosmos to be fact and then gave the book free to be read, already in 1621. We still have Galileo’s personal censored copy of the book. This censorship was only really effective in Italy the rest of Europe not taking much notice of the Church’s efforts to suppress heliocentricity.

This setback did very little to slow down Galileo’s rise to fame and he became a very favoured celebrity throughout Northern Italy. Symptomatic for this is his notorious dispute with the Jesuit astronomer Orazio Grassi over the nature of comets that peaked in the publication of Galileo’s Il Saggiatore, in 1623. A dispute in which Grassi was scientifically right and Galileo wrong, but in which Galileo carried the laurels thanks to his superior polemic and the sycophantic cheers of his high powered fan club, which included the newly elected Pope, Urban VIII, Galileo’s old friend Maffeo Barberini.

Barberini’s elevation to the Holy Throne gave Galileo the chance he had been waiting and longing for, the chance to go down in history as the man who established the heliocentric cosmos. Using his friendship with the new Pope, Galileo convinced Barberini that the German Protestants were laughing at the Catholic Church because it had rejected heliocentricity because according to those dastardly Protestants the Catholics were too stupid to understand it. Beguiled by his silver tongued friend Barberini gave Galileo permission to write and publish a book in which he would present both the Ptolemaic and Copernican systems to demonstrate the deep astronomical knowledge of the Catholics but by no means was he to favour one of the systems. Galileo wrote the book, his Dialogo, in which he was anything but impartial and unbiased, as instructed, but instead left nobody in any doubt just how superior the Copernican system was in his opinion, however he still lacked any real empirical proof. Through a series of tricks he managed to get his book past the censors and into print. Galileo had erred very badly, you don’t play the most powerful absolutist ruler of your time for a fool, particularly not when that ruler is already displaying strong signs of the paranoia that, sooner or later, effects all absolutist rulers.

I’m not going to go into all of the contributory factors that played a part in the sorry mess that was Galileo’s trial by the Inquisitions, I’ll deal with those one day in another post, but it is safe to say that he got stamped on for his hubris. By comparison with other cases he didn’t actually get stamped on very hard and got off relatively lightly. I can already hear the screams of protest at the last sentence but within the context of the times and place where Galileo lived and moved it is an accurate description of his fate.

One thing that should be made very clear when discussing this whole sorry mess is that Galileo was never the fearless defender of scientific truth or freedom of speech that his modern fan club like to present him as. He was an extremely egotistical social climber with an eye on the main chance, his own undying fame. Through his ill-considered actions he achieved his goal but not quite in the way he had intended.

It is ironic that many people today still believe erroneously that Galileo actually proved the reality of a heliocentric cosmos in his Sidereus Nuncius.

[The original opening paragraph of this post was modified at the request of those who wish it to be used as a short simple reference source]


Filed under History of Astronomy, Myths of Science, Renaissance Science

36 responses to “Galileo, the Church and Heliocentricity: A Rough Guide.

  1. We focus on Galileo in explaining how this all played out; but the personality of Urban VIII, Maffeo Barberini, had a lot to do with it. The Pope was famous in his own time for two things: nepotism and vanity. Since enriching your friends and relatives was standard operating procedure for a Pontiff of that era, you can imagine how good at it Barberini had to be at to earn a special reputation. The bar was set pretty high. No wonder Galileo devoted so much effort to cultivating a man who offered so much to a courtier on the make. Unfortunately, the Pope’s other characteristic, his vanity, made him a dangerous patron. Barberini believed himself to be a great poet; and, like the Volgon captain in a Hitchhiker’s Guide to the Galaxy, he was in a position to make you listen, no matter how much it hurt. You just don’t cross aristocrats, especially if they have literary pretensions. That Galileo was, among other things, a literary critic probably made his perceived disloyalty hurt all the more; and, after all, Galileo’s crime was always more lese majeste than heresy.

    • I agree totally Jim but I was saving that for the circumstances leading up to and surrounding that infamous trial

      • I hope this means a post about that is in the pipeline. I’m guessing also that’s why you included no discussion of Letter to the Grand Duchess Christina.

        Then again, I suppose you have already posted heavily on this topic, so I can’t blame you if you’re tired of it.

      • The title Rough Guide was meant to be taken seriously and also the statement “a minimum of explanation and justification”. This post is just an outline. The so called Letter to the Grand Duchess Christina is covered by the tenth paragraph; GG telling the Church how to interpret the Bible. The letter itself is actually incredibly tedious and when I don’t have to read and/or discuss it I’m happy.

  2. Brilliant post, Thony. Could use an extra comma here and there, I smiled at your original “he who should not be named &c” and knew exactly whom you were addressing…

  3. JF

    I like this post very much!

  4. Baerista

    Bravo Thony!

  5. Tim ONeill

    Bookmarked for future reference.

  6. A post that may enrage Thony’s and Baerista’s old sparring partner. He may parachute down any moment.

  7. Interesting that Cox mentions The Starry Sky when, on my desperately sparse knowledge, the case was based on the Dialogue. My understanding is that the Dialogue was initially titled On the Ebb and Flow of the Tides, but Galileo was forced to re-title it because his central argument was that there should be only one tide a day in a heliocentric solar system – which was patently wrong.

    I am familiar with e.g. Aiton ( , or Brown ( Is there a reason why there is rarely a mention of this feature of the case?


    • Thanks for the reference to Aiton; his The Vortex Theory of Planetary Motions is a gem. As for Galileo’s tidal theory, I’d also recommend Shea’s “Galileo’s Claim to Fame: The Proof That the Earth Moves from the Evidence of the Tides”, British Journal for the History of Science, Vol. 5, No. 2 (Dec., 1970), pp. 111-112. And I guess I should recommend Telescopes, Tides, and Tactics by the doyen of Galileo studies in English, Stillman Drake. But I must admit it’s still on my to-read list.

      Brown’s paper I find remarkable, in that he defends Galileo’s theory by suggesting Galileo was even more of an Aristotelian than usually thought: different dynamical laws for earth, water, air, and fire. Brown’s theory is criticized in Naylor’s “Galileo’s Tidal Theory”, Isis, Vol. 98, No. 1 (March 2007), pp. 1-22. (Unfortunately, when I glanced at it again just now, I found my memory of the details sadly lacking. Hopefully my description is still correct.)

      Heilbron mentions in his Galileo bio that Galileo’s early friend (mentor?) Paolo Sarpi had written a book with the identical title, Dialog on the Flux and Reflux of the Tides many years earlier; possibly that may have influenced Galileo’s preferred title. Naylor has also recently written an article Paolo Sarpi and the first Copernican tidal theory; alas, I don’t have access to the full article, but the abstract looks interesting.

    • Oh yes, when you said

      Galileo was forced to re-title it because his central argument was that there should be only one tide a day in a heliocentric solar system –which was patently wrong.

      this isn’t quite correct. This “one tide a day” theory was a feature of all tidal theories before Newton. (Nor was Galileo one to let an inconvenient fact slay a beautiful theory.) The problem from the censor’s viewpoint was that Galileo’s preferred title put too much emphasis on a supposed proof of Copernicanism. So he demanded that it be changed. The scientific problems with Galileo’s theory went well beyond the “one tide a day” issue.

      • This “one tide a day” theory was a feature of all tidal theories before Newton.

        This statement, Michael, is I’m afraid to say complete rubbish. Most people were fully aware that there are two tides a day and it was also widely recognised that there is significant correlation between the moon and the tides. However supporters of the lunar-tides theory, such as Kepler, were unable to produce a causative factor in support of their theory until Newton showed it to be the force of gravity.

      • @thonyc
        Let me rephrase. No tidal theories before Newton explained why there are two tides a day rather than one. Thus the Sarpi-Galileo theory was not at a disadvantage in this respect (though it had other problems).

        I’m surprised you came up with such a strange interpretation of what I wrote. The features of a theory include not just its successes, but also problem areas of prediction-observation mismatch. The Kepler lunar theory predicts a bulge of water below the moon, but no bulge on the other side of the earth. Thus one tide per day. At least the one tide is correlated with the moon, an advantage over the Sarpi-Galileo theory.

      • I should add that Galileo and (probably) Kepler both proposed a fix for the 2-to-1 discrepancy: in modern terms, resonance. (Galileo’s discussion is a bit clearer than Kepler’s.) Not a crazy idea, since modern detailed tidal theories do include resonance effects, but still not the correct explanation of the twice-daily tides. Kepler also mentions “an additional reason”: the tides are caused by the breathing of the earth.

  8. MarylandBill

    I wish more people would read this stuff. It was just a year ago that I was at the Smithsonian’s Air and Space Museum with my family and one of the presenters there was trying to tell me that Galileo proved the heliocentric model of the Solar System. He was at quite a loss when I tried to correct him.

    • laura

      I read a piece put out by the Smithsonian awhile ago about Riccioli’s names for the craters on the moon in which the author was pretty flabbergasted that Riccioli didn’t give Galileo a bigger crater than than Tycho Brahe given how Galileo was obviously the greatest scientist of the 17th century and Tycho merely an “eccentric” peddling a weird, wrong model of the world. Not terribly impressive stuff.

      • I wonder what he thought about the fact that Clavius’ crater is much bigger than Galileo’s ;))

      • laura

        It’s actually a bit ironic. I was reading Delambre’s L’Histoire d’Astronomie Moderne this week and discovered that Delambre was indirectly responsible for the Smithsonian foundation. He’d be turning in his grave at this stuff!

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  10. Jeb

    “Galileo was obviously the greatest scientist of the 17th century and Tycho merely an “eccentric” peddling a weird, wrong model of the world. Not terribly impressive stuff.”

    Thus is the genius socially constructed. Conversely you can attempt to topple someone off the marble plinth by selecting a text when things were softer and more uncertain and suggesting bad ideas are simply repeating themselves.

    May not be impressive but its certainly effective in capturing peoples imagination without having to expand much energy in developing a narrative, its so easy to make this stuff up.

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  16. Thanks for a fascinating article!

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  22. Henry Higgins

    @thonyc Have you read Arthur Koester’s “The Sleepwalkers” (Hutchinson 1959)? It gives a good account of Galileo’s failings.

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