Galileo Galilei (1564–1642) was responsible for bringing the Copernican system more recognition. In 1632, Galileo published his book Dialogue Concerning the Two Chief World Systems. The book was written in Italian and featured a witty debate among three people: one supporting Aristotle’s system, the second a supporter of Copernicus, and the third an intelligent layman. The Copernican easily won the debate. The book was approved for publication in Florence but was banned a year later. Pope Urban VIII, a long-time friend of Galileo, believed that Galileo had made a fool of him in the book. Galileo was tried by the Inquisition and placed under house arrest for the rest of his life. All of his writings were banned.

Galileo was also famous for his work on motion; he is probably best known for a thought experiment using the Leaning Tower of Pisa. He argued that a heavy rock and a light rock dropped from the tower would hit the ground at the same time. His arguments were based on extensive experiments on balls rolling down inclined ramps. Many scientists believe that Galileo’s work is the beginning of true physics.