For centuries it was accepted that the Earth was standing still in the centre of the Universe while all other celestial bodies orbited it. This geocentric vision started to change with Nicolas Copernicus, who (in 1514) proposed a mathematical model in which the Earth and the other planets orbited the Sun. This became known as ‘Heliocentrism’. Initially the dispute between geocentrism and heliocentrism was mainly philosophical and theological argument however, Galileo soon changed that.
Convinced that Copernicus’ model was true, he started to test that theory by observing the sky with his newly developed telescope. Observing that Venus had phases like the moon led him to support heliocentrism. This resulted in several problems with the Catholic Church. In his first trial, in 1616, the Church forced him to present his theory as mere hypothesis. However, Galileo did not oblige and wrote a book describing his observations. He was then summoned to Rome to explain himself. In another trial he had to publicly declare that the Earth did not orbit the Sun and that he would never say so again. In addition, he was condemned to house arrest for the rest of his life. Nor could he receive any visitors with whom to discuss scientific ideas. The Pope also prohibited any reprinting of his previous books, to make sure his work would slowly disappear. Fortunately, that was not the case.
With the passing years, Galileo became blind and finally died in January 8, 1642. Only in 1992 was a review of his case ordered by the Pope John Paul II. Its conclusions led the Church to officially recognize Galileo’s discoveries and declare that there had been a misunderstanding. One of the conclusions was that one should not “unduly transpose a question of factual observation into the realm of faith”.