Hello, guys!
I need some help. I'm having a discussion with a guy who claims that the Catholic Church officially accepted heliocentrism only seventy years ago. I pointed out to him that in 1822. Pope Pius VII made a decree that books on heliocentrism can be printed in Rome, but he won't budge, saying that this isn't an action of acceptance. Can someone bring light to this issue?
You can get a detailed analysis of the stages of the rejection of Ptolemy's model in Michael Flynn's humorous but useful series of blog posts:
The Great Ptolemaic Smackdown. But basically the sequence of events was:
In 1616 and 1632 the consensus of scientists was firmly on the side of the Church and against the opinion of Galileo and a handful of other heliocentrists.
In 1651 Giovanni Battista Riccioli publishes his
New Almagest, summarising the arguments for and against heliocentrism and coming down in favour of the Tychonian Model over both the Ptolemaic and Copernican systems.
In 1664 Pope Alexander VII publishes the
Index Librorum Prohibitorum Alexandri VII Pontificis Maximi jussu editus which includes all previous condemnations of heliocentric books.
In 1687 Newton publishes his
Principia Mathematica, reconciling a new physics of motion with Kepler's Laws of Planetary motion, doing away with most of the physical objections to heliocentrism.
In 1742 an annotated copy of Newton's
Principia was published in 1742 by Fathers le Seur and Jacquier of the Franciscan Minims, two Catholic mathematicians, with a preface stating that the author's work assumed Heliocentrism and could not be explained without the theory.
In 1744 a "corrected" copy of Galileo's Dialogue is printed in Italy - it is basically Galileo's book, but with the word "if" inserted in some of the marginal topic headers.
In 1758 the general prohibition of books on heliocentrism was dropped from the Index, though prohibitions on "uncorrected" copies of Galileo and Copernicus' works remained.
In 1791 Giovanni Guglielmini, a professor of mathematics at the University of Bologna, drops weights from the Torre dei Asinelli in Bologna and find evidence of a Coriolis deflection, thus providing direct empirical evidence of the rotation of the Earth.
In 1806 Giuseppi Calandrelli, director of the observatory at the Roman College publishes
Ozzervatione e riflessione sulla paralasse annua dall’alfa della Lira, reporting parallax in α-Lyrae. This provides a simple direct observation of the revolution of the Earth.
In 1820 the Church censor Filippo Anfossi, refuses to license a book by a Catholic canon, Giuseppe Settele, because it openly treats heliocentrism as a physical fact. The Congregation of the Index reconsiders the ban on an appeal by Settele and it is overturned.
In 1822 Pius VII approves a decree by the Sacred Congregation of the Inquisition to allow the printing of heliocentric books in Rome.
In 1835 that year's new edition of the
Index omits Copernicus's
De Revolutionibus and Galileo's
Dialogue.
I have no idea where your guy got "70 years ago" from. As you can see from the timeline above, the process was a gradual one as the science became more clear, but if there is one date that we can use to say they changed their view then it is, as you say, 1822. It's sometimes claimed that the Church only finally accepted heliocentrism with John Paul II's speech on October 31, 1992, addressing the special report on the Galileo Affair he had commissioned, which was widely but badly reported at the time as "the Pope finally admits Galileo was right". But John Paul II's speech actually just summarised the history behind the dispute with Galileo and commented on the relevant theology. The acceptance of heliocentism came 195 years ago, not 70, and there had been a tacit acceptance of it since about 1742.
