This essay is the first in a series which explores historical encounters which are often presented as conflicts between science and Christianity.
This article has been expanded – the full version can be found here.
“The laws of nature are written by the hand of God in the language of mathematics” – Galileo Galilei (Il Saggiatore, 1623)
Galileo Galilei (1564 – 1642) was a brilliant mathematician, astronomer and physicist. He was appointed to the chair of Mathematics at the University of Pisa in 1589, and spent the next 20 years conducting excellent astronomical observations and making significant discoveries in pure and applied science. He did groundbreaking work in the mechanics of falling bodies under gravity (although, contrary to that other myth, he never dropped anything off the Tower of Pisa), and made significant improvements to the design of telescopes. In 1610 he published his observations of the moons of Jupiter, and it is at this point that our interest in him really starts.
Astronomical understanding in the early 17th century was still rooted in the Aristotelian model, the core of which was that the heavens were composed of concentric circles, with the Earth at the centre. The celestial bodies themselves were perfect circles made of “incorruptible aether” and were eternal – subject neither to generation nor decay.
This was the reigning scientific model which the secular universities were adamant to maintain, but Galileo’s observations of sunspots and lunar craters cast doubt on the “perfect circles”, and his observation in 1604 of a supernova contradicted the immutability of Aristotle’s heavens. Moreover, his observations of Jupiter’s moons challenged the notion that all celestial bodies orbit the Earth. Galileo endorsed the heliocentric system developed by Nicolaus Copernicus, a Catholic priest who published his De revolutionibus orbium coelestium in 1543.
In 1611 Galileo travelled to Rome to present his findings, and was greeted with great acclaim. He demonstrated his observations of Jupiter to Christopher Clavius, a Jesuit at the Collegio Romano and the most respected astronomer in Europe at the time, who confirmed Galileo’s observations and parts of his theses of planetary motion.
The secular university professors were not as accommodating to this activity as the Jesuits had been, however. After several years spent as a public advocate for the Copernican theory, Galileo wrote in his famous Letter to the Grand Duchess Christina in 1615 that his theories had “stirred up against me no small number of professors”, and that these academics had agitated strongly for ecclesiastical support in their cause.
This letter is also an excellent illustration of some personal aspects of Galileo. He was monumentally arrogant, belligerent and abrasive towards any who opposed him. He wrote concerning the professors:
“I should pay no more attention to them than to those who previously contradicted me – at whom I always laugh, being assured of the eventual outcome.”
It was in this letter, also, that Galileo himself defined the astronomical debate as being irrevocably rooted in interpretation of the Bible. Under pressure from both sides of the dispute, the Church was drawn into the fray. Cardinal Maffeo Barberini, the future Pope Urban VIII and a friend of Galileo, cautioned him to drop the matter. Cardinal Roberto Bellarmino, the “Consultor of the Holy Office and Master of Controversial Questions” (don’t you just love that title?), wrote a letter to Galileo in April 1615 outlining the Church’s official position. He pointed out that Copernican theory was perfectly acceptable as a working hypothesis, and if there were proof that the earth circles around the sun, “then we should have to proceed with great circumspection in explaining passages of Scripture which appear to teach the contrary.”
In effect, he challenged Galileo to offer some proof for his theory or stop pestering the Church publicly with it, but that if proof were offered he was open to hearing it.
(Interestingly, the heliocentric model had been considered by Aristotle and rejected – he wrote that under such a system we should see stellar parallaxes. In other words, the change of position of the earth from one side of its orbit to the other should change the relative positions of the stars in different seasons. The scientific strength of this objection is illustrated by the fact that stellar parallax was only observed in 1838 by Friedrich Bessel.)
Galileo had no astronomical proof to offer, partly because his own observations did not align properly with his theory. He insisted that planets move in perfect circles (based on Aristotle’s hypothesis) and rejected the theories of Johannes Kepler, who proposed in his Astronomia nova (1609) that planetary orbits are elliptical. Instead, Galileo proposed as proof a flawed and unconvincing theory that the tides were evidence of the Earth’s rotation (and, incidentally, specifically denying that lunar attraction was involved). In 1616 the Church ordered him to cease and desist his public advocacy of the unproven theory.
For the next seven years, Galileo acquiesced to the Church’s injunction, but in 1623 his friend and supporter Maffeo Barberini ascended to the papacy, and Galileo confidently re-entered the public fray. In the same year he published Il Saggiatore (“The Assayer”), in which he launched a vicious assault on a treatise on comets by Orazio Grassi, a Jesuit mathematician at the Collegio Romano. Grassi used observations of parallax to argue that comets are further away than the moon; Galileo ridiculed this idea and claimed rather that comets are an optical illusion. His factual error notwithstanding, the harshness of Galileo’s tone permanently soured his relations with the Jesuit order. Pope Urban VIII thoroughly enjoyed the rhetorical flourishes of Galileo’s prose, however, and composed a poem in his honour.
Like Galileo, Urban was a vain and irascible man. After listening to Galileo’s arguments for years, he declared that the possible ways of arranging the universe were so numerous that it was impertinent for mortals to claim that they had discovered the unique truth. He insisted that Galileo include the Aristotelian alternative in his presentations of the universe.
In 1632, Galileo published his response to these arguments: Dialogue Concerning the Two Chief World Systems. In it, he presented his astronomical theories as a conversation between Salviati, who is referred to as “the Academician” and represents Galileo’s own views; and Simplicio (or “The Fool”), who bumbles about and contradicts himself as he ineptly offers a straw-man version of the Aristotelian / Ptolemaic perspective – and more importantly, represents the Pope’s views.
Not too surprisingly, this didn’t go down very well with the Pope. His hubris and vanity would not tolerate public ridicule, and Galileo was called before the ecclesiastical court. He was condemned by the Catholic Church as “suspected of heresy” – about the strongest charge that could be brought, since Copernicanism had never been declared heretical – and was then whipped tortured killed burned housed with a personal valet in a luxurious apartment overlooking the Vatican gardens. He spent the remainder of his life in comfort (albeit technically under house arrest), working on his final masterpiece, Discourses and Mathematical Demonstrations Relating to Two New Sciences. Published in 1638, this book was the grand summation of much of his work in physics over the preceding thirty years.
So what shall we make of this tale? Although our 21st century perspective makes us indignant that the “truth” was being muzzled and declared heretical, I think there are some important misconceptions in that attitude:
- First, the obvious: Despite the fact that prominent atheists love to invoke Galileo as an example of the supposed “conflict” between science and religion, Galileo was a Christian. He responded to the secular professors who attacked his theory from a distinctly Christian perspective: in Letter to the Grand Duchess he invokes arguments by St Augustine and Thomas Aquinas regarding Biblical interpretation.
- Although we view Galileo’s theories as an obvious improvement over the Aristotelian model of a geocentric solar system, it is important to reiterate that this was not provable by Galileo’s own evidence. His observations of the moons of Jupiter and the craters of the moon suggested problems with the pure geocentric model, but he certainly could not prove his case. In fact, an objection could have been made on purely scientific grounds that the heliocentric model offered insufficient improvement in explanatory power to justifiably replace the reigning paradigm.
- I make no excuses for the Pope’s abuse of his position to silence a critic, but the church’s treatment of Galileo was remarkably restrained by the standards of 17th century Europe. Giorgio de Santillana, Professor of Humanities at MIT, wrote that “We must, if anything, admire the cautiousness and legal scruples of the Roman authorities”. The philosopher Alfred North Whitehead wrote:
“In a generation which saw the Thirty Years’ War and remembered Alva in the Netherlands, the worst that happened to men of science was that Galileo suffered an honourable detention and a mild reproof, before dying peacefully in his bed.”
Consider, in closing, this analogy:
John is a brilliant employee in a major corporation. He is also in charge of producing the company newsletter. The CEO of the company holds a view that John disagrees with. John publishes an article featuring a caricature of the CEO named “Retard Boy”. He gets fired.
The point in that scenario is not whether John’s views will eventually be proved right by later scientific discovery – he still exercised supremely poor judgement.