1. The basic controversy actually stems from the excellent and Church-honored astronomical work of Nicholas Copernicus (1473-1543). Copernicus was a canon in the Church, and may have even been a priest, but there is no direct evidence that he was ever ordained.
2. In 1543, Copernicus published 6 works on the Celestial Orbits, and it is here that the sun was placed at the center of the system, and hence we have our heliocentric understanding. Copernicus' work was dedicated to Pope Paul III.
3. Protestants attacked the Copernican system continuously, because they believed it violated Holy Scripture. However, There Was No Catholic Condemnation of the system in any way, shape, or form until the Galileo case came up in the early 17th century.
4. In the early 1600s, Galileo provided more evidence in support of the Copernican system, for which he was originally honored by the Church in 1610/1611.
5. In 1612, Galileo published "Letters on the Sunspots," and in this work, Galileo formally promoted the Copernican system. Shortly thereafter, Galileo received a congratulatory letter of support from Cardinal Barberini. Barberini later became Pope Urban VIII.
6. At that time the theory was not definitively proved, but it was looked upon, even by the Church, as a hypothetical possibility and so it could be taught that way. This fact is frequently ignored or falsified by opponents of the Church who wish to make it look like the Church is opposed to the findings of science.
7. Galileo was more convinced that the heliocentric theory was absolutely true, so he did not want to promote it as a hypothetical theory. Nevertheless, in support of his claim, Galileo stated that the movement of the ocean tides was proof of the earth's motion, which is quite silly. Galileo was also unable to refute some of the remaining claims made by those who still favored the Ptolemaic system concerning the problem with earth movement and the observation of the stars. Still, Galileo was convinced despite not having as much proof as necessary (and which would ONLY come about much later after Galileo died).
8. Galileo went even further and insisted that scripture needed to be reinterpreted to align itself with the as yet unproven Copernican system. Now he stepped on Church authority, and this led to the unfortunate developments on and off over the next 20 years or so, but Galileo was not the innocent victim that inaccurate and propaganda-based “history” often portrays to be as one who was severely persecuted only for telling the truth.
9. At this time (circa 1615/1616), the Protestant Reformation was in full swing, and one of its primary and false charges against the Catholic Church was a "lax interpretation" of scripture. However, with this in mind, the Church was much more circumspect and more reluctant to suggest reinterpretations based on theories that were still in a hypothetical state.
10. There were Church leaders at that time who were open to a reinterpretation