Why was Galileo persecuted by the Catholic Church?

Answer 1

Galileo was not truly 'persecuted' by the Church. However, he was told to stop teaching the heliocentric theory of the Universe because it was, at the time, unproven. Even Copernicus, another scientist (and a priest) who predated Galileo in his studies of the heliocentric theory, agreed that it was unproven and could not be proven with the technology of the time. What got Galileo into trouble was his tongue and his pen. He had a very sarcastic temperament and made some very nasty verbal attacks on the pope, who was a close friend and supporter. It might be pointed out that the Church supported Galileo in his work and most Church leaders agreed that the earth was most likely not the center of the Universe. However, no information had been brought forward that could prove this beyond a doubt.

After Galileo's time science advanced to the point where it had to be accepted that the Sun is at the centre and the Earth orbits round it. 200 years after Galileo's death, the German astronomer Friedrich Bessel made observations on a nearby star and found that it moved very slightly one way and the other against the background of distant stars, every six months, in time with the Earth's motion round the Sun.
Galileo was teaching the heliocentric theory of the universe as fact when it was, at the time, unproven. The Church asked him to revise his teaching to reflect that it was not a fact but only a theory or hypothesis. Most Church officials were on Galileo's side but agreed that he should tone down is rhetoric. Galileo had a very sharp tongue and was quite sarcastic in his remarks and that did little to help his case.

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Catholic AnswerGalileo was teaching the heliocentric theory of Copernicus as fact. Cardinal Bellarmine disagreed with him and said that it disagreed with Scripture. Galileo, though, was a personal friend of the Pope at that time. The Inquisition looked into the case and told him that he could teach, but only as a theory until he had some proof - which he didn't. Galileo agreed, then turned around, and ignored his solemn word to the Inquisition, figuring that he knew better, even though he still had no proof, he continued to teach Copernicus theory as fact. The Inquisition arrested him for violating his sworn word, and held him in a rather comfortable accommodation. Galileo berated everybody, including his friend, the Pope. He did not exactly endear himself to anyone, even though everyone was trying to help him! For more of the story, see the link below at the Catholic Encyclopedia.
Galileo was tried and sentenced by the Catholic Church for his work promoting the idea of a heliocentric universe. Before mankind became aware that the earth and other planets revolve around the sun, people believed that the sun and stars revolved around the Earth.

Answer 2

Roman Catholic Answer: Galileo was sentenced to house arrest in 1634 and told to recant. He lived in his country house for the rest of his life, although due to several illness he was allowed to travel for medical reasons. He died in 1642 from a fever. He was a loyal son of the Church.