Nobody expects the Spanish Inquisition: Galileo as a victim of the political Counter Reformation

The BBC reports that faculty and students at La Sapienza university in Rome are protesting a visit by the pope planned for later this week. Dr Joseph Ratzinger – aka Pope Benedict XVI – was due to give a keynote speech on Thursday at celebrations to mark the beginning of the academic year. The programme has since been changed so that the pope will now give an ordinary talk.

Sixty-seven academics signed a letter saying the Pope’s views on Galileo Galilei “offend and humiliate us”. When he was head of the Inquisition (known today as the Congregation for the Doctrine of the Faith), Ratzinger defended as “reasonable and just” the trial for heresy of the Italian astronomer-priest who first presented evidence that the Earth is not the centre of the universe.

Students at La Sapienza have organised four days of protest this week, which include an “anti-clerical lunch of bread, pork and wine” (?). One of their banners reads: “Knowledge needs neither fathers nor priests”.

I couldn’t agree more, only there’s a small problem with the popular interpretation of the Galileo story. The astronomer did not, as is commonly claimed, relegate the Earth from its privileged position, and thus offend the religious authorities. The truth is a little more complex than that, and has as much to do with inadequate scientific measurements and 17th century politics as theology.

In his recently-published Physics Today article, “The Copernican Myths”, physicist Mano Singham points out that in the early 16th century, the centre of the universe was considered to be a “squalid basement where all the muck collected.” Robert Bellarmine – cardinal, Jesuit, Doctor of the Church and persecutor of Galileo – said that “the Earth is very far from heaven and sits motionless at the centre of the world.” And in Dante’s Divine Comedy, hell is placed at the planet’s innermost core.

In challenging Ptolemaic astronomy, Galileo – whose ideas were based on a combination of his own astronomical observations and the ideas of Nicolaus Copernicus (published in 1543 as “De Revolutionibus Orbium Cœlestium”) – was in fact promoting the Earth’s position in the cosmos.

Singham quotes from an academic paper from 2001 by Dennis Danielson. In “The Great Copernican Cliché”, Danielson says that revisionist claims began to appear from around 1650, and by 1850 had become the popular consensus. Galileo stood trial in 1633.

We also need to look at how Galileo’s ideas were received at the time, and the nature of scientific revolutions in general.

The heliocentric model of the universe initially created as many scientific problems as it solved, and on a philosophical level it met with resistance from the academic establishment. The new model threw common-sense frames of reference into disarray, and scholars wondered how, if the Earth were not at rest, objects thrown upwards could fall back to the same point.

Copernican ideas did take hold among 16th and 17th century astronomers, but primarily because they made certain calculations easier. The heliocentric model was seen as a numerical hack rather than some profound truth about the nature of the cosmos.

With a lack of reliable data on planetary orbits, and an inability to grasp the idea of elliptical as opposed to strictly circular orbits, Copernican astronomy failed in its early years to give better numerical results than the Ptolemaic model. Where the Copernican model succeeded was in its aesthetic qualities.

Thirty years ago, Imre Lakatos noted that new scientific theories rarely give better results than their predecessors. What normally happens is that aesthetic appeal attracts followers, and provides the inspiration to pursue and improve the research. Only after exhaustive testing is a paradigm-breaking theory fully accepted, and in some cases this can take decades.

Singham notes that the religious objections to Galileo also differ from enlightenment folklore. The astronomer was initially given official support from the Church, and encouraged to publish. It was the rise of Protestant Christianity and subsequent political turmoil that did it for Galileo.

Martin Luther first denounced Copernicus in 1539, some 25 years before Galileo was born. The Copernican model contradicted the bible, and biblical literalism was the defining characteristic of the fast-growing Protestant movement.

There were a number of theological difficulties raised by heliocentric astronomy, but given the casuistical nature of theological reasoning, they were not insurmountable. It was the realpolitik of the Counter Reformation that finally led to the suppression of Copernican ideas.

Thomas Kuhn referred to this back in the late 1950s, yet to this day we remain saddled with the Copernican myths. The irony is that scientific evidence led the Protestant churches to rapidly abandon their opposition to the heliocentric model. The inertia-ridden Catholic Church, on the other hand, took until 1835 to lift its ban on De Revolutionibus, and Galileo’s reputation was not finally restored until 1992.

“In the name of the secular nature of science we hope this incongruous event can be cancelled,” say the La Sapienza professors in their letter of protest to the university rector. Yes, but we would better honour the memory of Galileo Galilei by getting the history right.

Update (16 January 2007)

It looks like the La Sapienza protesters have won this battle, as the pope’s visit has since I wrote this piece been called off. The “rational and just” quote, by the way, actually comes from the anarchist, unbelieving philosopher of science Paul Feyerabend. The irony of it!