AUTHOR: GALILEO GALILEI
DATE: 1632
The Dialogue Concerning the Two Chief World Systems is a landmark scientific treatise that enabled the world’s transition from one widely held view of itself to an entirely different one. It challenged the teachings of the Roman Catholic Church that, at the time, dominated much of European thought, and made the life of its author – the Italian astronomer, engineer and physicist, Galileo Galilei – very uncomfortable. But today no serious reader veers from its dominant idea that the Earth is not the centre of the Universe, but in fact the Earth and the other planets orbit the Sun.
The treatise builds on the work of the Polish-born Nicolaus Copernicus (1473–1543), especially his 1543 opus, On the Revolutions of the Celestial Spheres, which outlined a vision of the cosmos contrasting with the Ptolemaic system that puts our planet at the centre of everything – and which had dominated religious and scientific teaching since ancient times. It had immediately sparked the criticism of major religious figures, both Catholics and Reformists, who believed its radical thesis was at odds with scriptural teaching. For instance, Martin Luther is said to have noted: ‘This fool wishes to reverse the entire science of astronomy; but sacred Scripture tells us [ Joshua 10:13] that Joshua commanded the sun to stand still, and not the earth.’
Copernicus wrote in a style almost impenetrable to all but the most scientifically minded. With the religious establishment firmly set against him, his work failed to seep into the popular consciousness. Nonetheless, it did find wide readership among the scientific community (although reference to it was often caveated that it was a useful theoretical model, not one fixed in reality). It was also placed on the Catholic Church’s Index of Forbidden Books in 1616, where it remained for over a hundred and forty years.
The Pisan-born Galileo had become convinced of Copernicus’s ideas as a result of a raft of astronomical observations he made around 1609. He had then written to one of his students in 1613 about how Copernican theory might be reconciled with certain biblical passages, and the letter had brought him to the attention of the Inquisition in Rome. The Inquisition concluded that Copernican heliocentrism was heretical, not to mention ‘foolish and absurd’, and Galileo was warned to cease its promotion. But when Pope Urban VIII took over at the Vatican in 1623, Galileo found himself with an unexpected friend – one who gave his blessing to Galileo to write an exploration of heliocentrism as long as he didn’t come out for its adoption.
BANNED!
The Roman Catholic Church introduced its Index Librorum Prohibitorum (‘List of Prohibited Books’) in the first half of the sixteenth century, just as developments in printing technology were creating a new, much bigger audience for literary material. The list would go on to include all manner of works, from fiction and philosophy to scientific papers and unapproved versions of the Bible. Thousands of books came to be blacklisted for their potential to be ‘disruptive’ to the Church and wider society. It was only in 1966 that the Index was formally done away with during the tenure of Pope Paul VI – a mere five years after Simone de Beauvoir’s The Second Sex became one of the last modern classics to fall foul of the censors.
The result was The Dialogue, published in 1632 with the assent of the Inquisition. The book is structured as a conversation held over several days between two philosophers – Salviati, who argues Copernicus’s corner, and Simplicio, who stands with the Ptolemaic worldview – and a neutral layman, Sagredo. They debate the various merits of each side, frequently through the use of thought experiments. For instance, if the earth is in motion, should not a cannon-ball fired in one direction land further away than if fired in the opposite direction?
While Galileo aimed for a neutral tone, and declared the subject matter of the book as ‘hypothetical’, it was quite apparent to most observers what side of the argument he was on. Nor did it help that Simplicio – a name that conjures up the very notion of a ‘simpleton’ – is frequently the subject of ridicule. When Galileo finished the book in 1630, it was due to go before the censors in Rome and would not likely have passed them unamended. But because of an outbreak of the plague, he was allowed to send it to the censors in Florence instead, who proved a rather easier audience.
Yet he would not get an easy ride for long, not least because Urban VIII felt offended at having his side of the argument represented by a figure such as Simplicio. In 1633 Galileo was brought before the Inquisition in Rome, who reminded him of the earlier admonition to abandon Copernican theory. Galileo claimed he had only discussed the theory, not defended it, before agreeing that he was guilty of ‘overstating his case’. Judged ‘vehemently suspect of heresy’, he was forced to renounce his troublesome beliefs and the book itself was banned. Galileo was sentenced to imprisonment at the Inquisition’s pleasure, although in reality he was held under house-arrest (first at a friend’s palace in Siena and then in a villa in the Tuscan countryside) for the rest of his life. As his punishment was handed down, legend has it that Galileo repeated under his breath, ‘And yet it moves’, although the story is probably apocryphal.
Galileo was a giant of the scientific world on many counts – a pioneer of the scientific method, who brought together mathematics and theoretical and experimental physics to tackle age-old mysteries. After his altercations with the Vatican, he understandably largely steered clear of the subject of heliocentrism. It was only in the eighteenth century that the Church allowed the publication of The Dialogue and only in 1835 that it was formally removed from the Index in all its forms. But by then, Galileo had all but won the argument. The world had come to realize that our little planet is not, after all, the centre of everything. And despite that, the earth literally carries on turning. Speaking in 1939, Pope Pius XII even called Galileo one of the ‘most audacious heroes of research … not afraid of the stumbling blocks and the risks on the way, nor fearful of the funereal monuments’. True, and an acknowledgement better late than never.