Galileo used his mathematics knowledge and technical skills to build a telescope in 1609. Galileo’s observations strengthened his belief in Copernicus’ theory (published in 1514)that Earth and all other planets revolve around the Sun. Galileo expected the telescope to quickly make believers in the Copernican system out of all educated persons, but he was disappointed. The Catholic Church, which was very powerful and influential in Galileo’s day, strongly supported the theory of a geocentric, or Earth-centered, universe. In 1616, on orders of the Pope Paul V, Cardinal Bellarmine called Galileo to his residence and administered a warning not to hold or defend the Copernican theory; Galileo was also forbidden to discuss the theory orally or in writing. After repeated convincing attempts by Galileo, Pope Urban VIII allowed him to write about the Copernican theory as long as he treated it as a mathematical hypothesis.
In 1630 he completed his book Dialogue Concerning the Two Chief World Systems in which the Ptolemaic and Copernican models were discussed and compared. Vatican cleared (conditionally) to publish the book. The book was printed in 1632 which was quickly sold out and soon became the talk of the literary public. Enemies of Galileo had convinced the Pope that the Dialogue was nothing but a thinly-veiled brief for the Copernican model. Pope Urban VIII, convinced by the arguments of various Church officials, stopped its distribution; the case was referred to the Inquisition and Galileo was summoned to Rome despite his infirmities, to answer the charges in February 1633. Old Galileo travelled for twenty-three days in cold winter from Florence to Rome.
He was formally interrogated for 18 days and on April 30 Galileo confessed that he may have made the Copernican case in the Dialogue too strong and offered to refute it in his next book. Galileo was sentenced to life imprisonment. Because of his age and poor health, he was allowed to serve his imprisonment under house arrest until his death in 1642. The Church finally accepted that Galileo might be right in 1983.