By the middle of the eighteenth century, Newton’s version of the heliocentric theory had been universally accepted by all of those knowledgeable enough to express a considered opinion on the subject. However, some (most?) Jesuit astronomers continued to pay lip service to a variant of the Tychonic geo-heliocentric system, as their personal allegiance to the Pope required them to. This, of course, raises the question of the Catholic Church’s stand on the subject. You can find accounts that claim that the Church only accepted that the solar system is heliocentric in the nineteenth century, whilst other go as far as to claim that this back down first really took place with the Vatican’s examination of the Galileo case in the 1980s. Neither of these views is actually correct and is mostly the case it was in reality a long drawn out process that it pays to review, beginning with a brief recap of how it all started.
The whole story started in 1615/16 when Galileo Galilei and the Carmelite theologian Paolo Antonio Foscarini (c. 1565–1616) provoked the Catholic Church into making a serious assessment of its position on the heliocentric theory of the cosmos. Famously the Church’s examiners said that the theory contradicted by Holy Scripture and the then scientific consensus. In a famous meeting with Roberto Bellarmino, Galileo was instructed that he was not allowed to hold or teach the heliocentric theory as fact, a stricture that applied to all other members of the Church. Several books that did in fact present the heliocentric theory, as fact were placed on the Index of forbidden books, including, for example, those of Johannes Kepler. Interestingly, Copernicus’ De revolutionibus was only placed on the Index until corrected. This correction was carried out and only consisted of the removal or modification of a handful of passages that stated or implied that the heliocentric theory was true. By 1621 the thus mildly censored De revolutionibus was again accessible for Catholic astronomers to study.
Famously, Galileo then provoked the Church further in 1632 with his Dialogo that very definitely did teach the heliocentric theory as true with the well-known consequences. Although under the circumstances Galileo’s punishment was relatively mild and the Church left him in peace in his house arrest, even turning a blind eye when his Discorsi was published in 1638. However, when Galileo died the plans of the Grand Duke of Tuscany, Ferdinand II, to bury him in a specially erected marble mausoleum in his honour in the Basilica of Santa Croce in Florence, were basically stopped by the Pope and he was buried in a simple grave in a side chapel instead.
It is important to note that although the Church banned the heliocentric theory as a true model of the cosmos it was still permissible to discuss the heliocentric hypothesis. Outside of Italy the Church’s ban had very little effect even in Catholic countries and of course none in Protestant ones. In the seventeenth century, within Italy astronomers would discuss heliocentricity but starting their work with something along the lines of, the Holy Mother Church in its wisdom has ruled that the heliocentric theory is false, but it is an interesting mathematical hypothesis, which I will now elucidate. And so, both sides were happy. There are no major cases of astronomers being prosecuted for holding the heliocentric theory, although both the leading Catholic astronomers Pierre Gassendi and Giovanni Battista Riccioli were investigated by the Inquisition after being suspected of holding the heliocentric theory in their respective main astronomical works, Institutio astronomica (1653) and Almagestum novem (1651), where they discussed the heliocentric hypothesis helping to spread knowledge of it. No charges were raised in either case.
By the end of the seventeenth century, following the publication of Newton’s Principia Mathematica in 1687, it was fairly obvious that the heliocentric system had become the accepted model of the cosmos amongst astronomers, although as noted earlier empirical proof of the Earth’s movement had still not been found. In the early eighteenth century the Catholic Church’s stand on heliocentricity and Galileo began to slowly weaken. In 1718 the Inquisition’s ban on printing the works of Galileo was lifted and permission for an edition of his works was granted, which however excluded the Dialogo. In 1741, Pope Benedict XIV authorised a complete edition of his works including a lightly censored version of the Dialogo.
Meanwhile, in 1737 the Church gave permission for Galileo to be reburied. His corpse was removed from its grave in the side chapel and he was reburied in a spectacular tomb in the main body of the Basilica.
Bizarrely during this process, three fingers and a tooth were removed from his body and these are now displayed like some sort of religious relics in the Museo Galileo in Florence. This is all part of the Galileo as martyr for science and/or free speech that has grown up over the centuries.
In 1758 the general prohibition against publications on the heliocentric theory was lifted by the Pope but the books that had been placed on the Index for propagating the heliocentric theory remained there. Things remained quiet until 1820, when The Master of the Sacred Palace (the Church’s chief censor), Filippo Anfossi (1748–1825), refused to licence a book by the Catholic canon, Giuseppe Settele (1770–1841), which treated the heliocentric theory as factual. Settele appealed to Pope Pius VII, who referred the matter to the Congregation of the Index and the Holy Office, who after due consideration overturned Anfossi’s decision. Following this decision, the banned books on heliocentricity were removed from the Index when it was next revised in 1835.
Many supporters of science against, what they see as, the ignorance of the Catholic Church, who have a very narrow focus, demand to know why the Church did not remove its ban much earlier and at the same time rehabilitate Galileo. These people simply ignore the fact that the Catholic Church is one of the largest religious institution in the world, which regards itself as responsible for the whole of humanities existence and its actions. In this grand scheme of things astronomy and cosmology, whilst important, play, very much, a minor role, and as long as there is no immediate need to address any problems, they might not, then the Church has more important things to occupy its attention. Also, because of its sheer size and influence the Church took its time when changing a doctrine that would have a wide impact, after all the heliocentric theory does contradict Holy Scripture. For an institution that was already fifteen hundred years old when it had its initial disagreement with Galileo, a couple of centuries is not a long time.
As opposed to popular opinion Galileo, himself, had rather drifted out of the limelight during the seventeenth and eighteenth centuries; science had moved on and left him behind. However, at the end of the eighteenth century and the beginning of the nineteenth people began to elevate him to his current mythical status, as the martyr for science and/or free speech in the supposed eternal war between science and religion, which never actually existed. From this point on the demands for a rehabilitation of Galileo by the Catholic Church began to grow in volume.
As already observed the Church moves slowly in such matters and it was first in 1979 that Pope, John Paul II expressed the hope that “theologians, scholars and historians, animated by a spirit of sincere collaboration, will study the Galileo case more deeply and in loyal recognition of wrongs, from whatever side they come.” In 1992 issued a statement concerning the deliberation of the committee he had set up to reassess the conflict between the Catholic Church and Galileo in 1979. Contrary to popular belief this was not the Church admitting that they were wrong and Galileo right but an interesting fairly even handed assessment of the mistakes made at the time by the Church, which clearly states that there was blame on both sides, although he puts it somewhat more diplomatically:
A tragic mutual incomprehension [emphasis in original] has been interpreted as the reflection of a fundamental opposition between science and faith. The clarifications furnished by recent historical studies enable us to state that this sad misunderstanding now belongs to the past.
People will almost certainly go on discussing the conflict between Galileo and the Church for many years to come but I personally don’t think anything new can be won by doing so.