Discoveries and Opinions of Galileo

Born in 1564 in Pisa, Italy, Galileo was the son of music theorist Vincenzo Galilei. Galileo himself showed an early talent for music as well as painting, and in 1581 he began attending the University of Pisa with the intention of becoming a physician. He instead decided to pursue mathematics, against the wishes of his father.

A professor of mathematics from age 25, Galileo began conducting experiments on the laws of motion which led to his discovery of the law of falling bodies. The discovery contradicted Aristotelian physics and caused controversy with his colleagues at the school, who declined to renew his contract to teach there. Galileo instead found employment at the University of Padua, and during this period (beginning in 1592) his main achievements in astronomy began, as chronicled in Discoveries and Opinions of Galileo.

Galileo’s advocacy of the heliocentric model of the universe, which Copernicus originated, got him into increasing trouble. Some high church officials in Rome believed that the Copernican theory was incompatible with scriptural teachings about creation and providence. This was also an era in which Aristotle’s philosophy was widely held as normative, and many felt that the heliocentric theory had little evidence behind it. Galileo defended his ideas about science and religion in his “Letter to the Grand Duchess Christina.” Pope Urban VIII, a friend and supporter of Galileo, encouraged him to write about the Copernican model but to treat it as hypothesis rather than proven fact.

In 1632 Galileo’s book A Dialogue on the Two Principal Systems of the World was censured by the Holy Office (Inquisition), which held that Galileo had gone beyond the pope’s stricture. Galileo was tried and found guilty of heresy; he was compelled to abjure his teachings and sentenced to house arrest. While under arrest, Galileo completed his final work, on motion and gravity.

Many of Galileo’s contemporaries saw his condemnation as a tragedy. In time, his work came to be seen as fundamental to our understanding of physics, the structure of the cosmos, and the method of experimental trial and error that forms the basis of modern science.