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UCL Festival of Culture: Galileo: what was his crime?

By Siobhan Pipa, on 2 June 2016


Portrait of Galileo Galilei, Justus Sustermans

Nearly 400 years ago in April 1633 the Italian astronomer, mathematician and natural philosopher, Galileo Galilei was put on trial by the Roman Inquisition.

The main charge against him centred on his support for the Copernican theory, aka the belief that a mobile Earth orbited a stationary sun. The theory was thought to contradict the Bible and Galileo was placed on trial for heresy.

But what was Galileo’s real crime? Was science really defeated by religion, as legend would have it? These were some of the questions raised by Andrew Campbell from UCL Italian in his lecture Galileo: what was his crime?, organised as part of the UCL Festival of Culture.

I’ve always found the Galileo Affair fascinating and it’s often used as the leading example of the supposed battle between science and religion. Florence’s Galileo Museum proudly displays his mummified middle finger pointing towards the heavens – a definitive display of science triumphing over the Catholic Church.

When Galileo is mentioned today it’s often not in recognition of his scientific work but as the poster child for the war between religion and science. However, is it as simple as this – can you separate science and religion from the politics, and personalities, of the day?

To delve a little deeper into the whole affair Andrew provided a short run through of the events which led up to 1633.

100 years earlier the accepted model of the universe was the Aristotelian Ptolemaic geocentric model – the Earth is at the centre of all celestial bodies and the moon, the sun, all the planets (at least those discovered, sorry Uranus and Neptune), the fixed stars and the Primum Mobile circle the Earth.

There were some issues with this model. Planets sometimes appeared as though they were moving backwards, also referred to as retrograde motion (a term still used by followers of astrology).

However, vitally, geocentrism was supported by passages in the Bible. The Bible doesn’t explicitly state that the Earth is the centre of the universe but the theory does match some literal interpretations of scripture.

Geocentric celestial spheres; Peter Apian's Cosmographia (Antwerp, 1539)

Geocentric celestial spheres

In 1610 Galileo published the treatise, Starry Messenger, describing the observations that he had made with his new telescope. It was this pamphlet that saw Galileo shift from discussing heliocentrism as just a theory to stating it as fact.

This sparked a debate on whether Galileo’s reporting was heretical as it disagreed with scripture. Galileo argued that the heliocentric theory wasn’t contrary to the Bible. In a letter he claimed:

“The intention of the Holy Ghost is to teach us how one goes to heaven, not how heaven goes.”

This debate went back and forth – some defending Galileo, others not. Eventually in 1616 an inquisition was held, heliocentrism was deemed to be heretical and Galileo was ordered to abandon his defence of the theory.

Here’s where things get a bit sketchy. There are two versions of the verdict which was delivered to Galileo – one is worded incredibly strictly referring to not teaching the theory in any way, the other a bit more loosely and could be argued to allow hypothetical discussion.

Galileo being Galileo, chose to follow the latter. In 1632 he published the Dialogue Concerning the Two Chief World Systems, a sort of satirical account of a conversation between a Copernican scientist, an impartial scholar and an Aristotelian philosopher.

The Aristotelian philosopher argues for geocentrism and all his points are swiftly knocked down and disparaged by the other two. With the publication of this Galileo lost many of his allies in Rome, including the new Pope Urban VIII.

In April 1633 the Galileo was put on trial by the Roman Inquisition for heresy. The Inquisition found that the Dialogue argued for heliocentrism and Galileo had breached the agreement he made with the church in 1616. He was declared “vehemently suspect of heresy” and sentenced to house arrest.

There’s a lovely legend that exists, and one that really demonstrates Galileo’s personality, which claims that after officially recanting his work Galileo whispered under his breath, Eppur si muove — “Yet it moves”. Galileo died in 1642 still under house arrest.

The church’s stance on Galileo’s work has changed over time, in 1992 Pope John Paul II issued a declaration acknowledging the church’s errors. The next morning the papers proclaimed “Galileo was right”.

So what was his crime back in 1633? Galileo’s personality certainly didn’t make things easy – he antagonised the Pope, he was pretty arrogant and had a knack for getting people’s backs up. But myself, and the audience, agreed that at the very least it’s safe to conclude that Galileo wasn’t a heretic.

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