Galileo Galilei was an Italian Physicist, mathmatician, astronomer and a philosopher. He became known as 'The Father of Science' as he was the first man to confirm the phases of Venus and he also discovered the four largest satellites (moons) of Jupiter. These were later named the 'Galilean Moons' in his honour. Galileo's work remained controversial for many years as the general belief throughout the world of astronomy was that the Earth was the centre of the Universe.
In 1610, Galileo began to publicly announce his theory of heliocentrism (the idea that the sun is the centre of the Universe) when he was met with great opposition from fellow astronomers and clerics who eventually denounced him to the Roman inquisition in early 1615. Although he was cleared of any offense at the time, the catholic church nevertheless condemned his work and he was ordered to stop.
Later, in 1632, he began to defend his work when he published his book 'Dialogue Concerning the Two Chief World Systems'. He was again tried by the inquisition and found guilty of heresy and spent the rest of his life under house arrest.