If you are a regular reader of my outpourings you can skip this post, as I shan’t be saying anything that you’ve not already read, probably more than once, because we’re back to the topic of astronomy, cosmology, Galileo and the Church at the beginning of the 17th century.
Rob Knop is an astrophysicist who blogs under the title Galactic Interactions as part of the Scientopia blogging collective. His most recent post bears the provocative title In Which I Compare the Slashdot Commentariat to the 17th-Century Catholic Church. This is an impassioned rant aimed at those Internet commentators who dare to cast doubt on the existence of dark matter, an unforgivable sin in Professor Dr. Knop’s opinion. He accuses them of holding the opinion that they do, because, unlike him, they are not qualified astrophysicists and therefore do not know what they are talking about. I refrain from commenting on this part of Rob Knop’s rant, as he would only dismiss anything I might say on the grounds that I also am not an astrophysicist. However I will comment on the following section of his rant stated in his imposing title. Here he equates those who question the existence of dark matter with those who initially rejected heliocentricity, and in particular the leadership of the Catholic Church, at the start of the 17th century. He writes:
Much as… the 17th century Catholic church (sic) just knew that Galileo (and others) were wrong about Heliocentrism, because it’s obvious to everyday observation that the Earth is still and the Sun is going around it. (Also, the Bible says so.) And, just as the leaders of the Catholic church (sic) completely discounted (and indeed refused to look at) Galileo’s observation of Jupiter’s moons orbiting Jupiter (and, crucially, not the Earth)…
We are of course here in Draper-White territory, deep in the 19th century and the “war between science and religion”. It is indeed true that the Catholic Church rejected heliocentricity at this time because it conflicted with their theology but as I have pointed out more than once also because there was no proof for the heliocentric hypothesis and in fact serious empirical arguments against it. It is indeed obvious that the world in still and demonstrating otherwise proved to be very difficult, which brings us to the second half of the passage I have quoted above.
Galileo’s observations of Jupiter’s moons do not refute the Ptolemaic geocentric hypothesis or prove the Copernican heliocentric one, as Galileo well knew. In fact he was very careful never to claim that they did. What they do refute is the Aristotelian homocentric hypothesis, which is a completely different kettle of fish and which the contemporary Ptolemaic astronomers were not sorry to see go, as I have already commented long ago. Secondly the Catholic Church did not refuse to look at Galileo’s Jupiter observations, it is true that some senile prelate said that he did not need to look through a telescope to know that Galileo was wrong but one prejudiced fool in not the whole Church. In fact the Church in the form of Roberto Bellarmino, the leading theologian of the time, asked the astronomers of the Collegio Romano if they could confirm Galileo’s observations. This they could and did do, even inviting Galileo to a banquet in his honour to celebrate his discoveries. All of this Professor Knop he would have learnt as an undergraduate in history of astronomy 101 if he was a historian of science. This of course is the raison d’être for writing this post and for its title. Rob Knop criticises people who he considers to be unqualified for calling the dark matter hypothesis into question and then precedes to trample all over the history of 17th century astronmy a subject of which he is obviously totally ignorant.
As a sort of footnote I will point out that the German astronomer Simon Marius who discovered the moons of Jupiter one day later than Galileo, and whose observations of them were more accurate than his Tuscan rival’s, also rejected the heliocentric hypothesis preferring instead the Tychonic geocentric-heliocentric model with which the observations were totally compatible. My Internet friend and colleague Professor Christopher Graney is currently involved in a longer research project looking at which model of the solar system was more plausible in the 17th century given the available scientific evidence. Know what? His research shows very clearly that the evidence supports the Tychonic system over the Copernican!