1822: The College of Cardinals finally caves in to the hard facts of science, saying that the "publication of works treating of the motion of the Earth and the stability of the sun, in accordance with the opinion of modern astronomers, is permitted."

It represented a major shift in dogma for the Catholic Church, a concession that the Earth, in fact, might revolve around the sun. Unfortunately, it came 189 years too late to do Galileo Galilei any good.

Still, it would take another 13 years, until 1835, before Galileo's Dialogue Concerning the Two Chief World Systems – the work in which he defends the heliocentric theory – would be removed from the Vatican's list of banned books.

As a theory, heliocentrism had existed since the ancient Greeks, who were the first to determine that the Earth is a sphere in a sky full of spheres. It remained an unproven theory directly opposed to the geocentric view held by Ptolemy and Aristotle, and embraced by Rome, that the Earth is the center of the universe.

Galileo was greatly influenced by the Polish astronomer Nicholas Copernicus, who not only posited that the Earth revolves around the sun but that it makes a complete turn on its axis every 24 hours. The Catholic Church, however, considered the theory heresy, and Galileo was convicted by the Inquisition in 1633 and remained under house arrest for the rest of his life.

Nearly two centuries later, however, the weight of scientific evidence was so overwhelming that the College of Cardinals finally reversed itself and allowed the teaching of heliocentrism. Still, it would take another 170 years, until 1992, for a pope – in this case, John Paul II – to officially concede that, yes, the Earth isn't stationary in the heavens. Eight years after that, in 2000, John Paul apologized for the way the Catholic Church treated Galileo.

Source: Various