After improving the telescope and achieving magnifications of thirty or more, Galileo turned it towards the heavens. His observations provided strong evidence for the Copernican sun-centered system. His beautifully illustrated and accessible little book reporting in Italian, not Latin, The Starry Messenger, was a best seller, and prompted many others to see for themselves the new phenomena in the heavens. Galileo had been attempting to provide a new physics to support the Copernican sun-centered system when the telescope offered him a unique opportunity. His observations challenged the church-supported earth-centered system of Ptolemy in numerous ways. The moon was rough, mountainous, and earth-like rather than smooth, polished and perfect. Jupiter was accompanied by four entirely new "stars" that moved around it as the planets moved around the sun. Venus showed the kinds of phases impossible in the old system. And, everywhere he pointed the telescope he saw many new stars, even in the diffuse brightness of the Milky Way. Telescopes and observers proliferated, and within only a generation the Copernican system displaced the Ptolemaic, even though many problems remained to be solved. His work on the physics of the Copernican system was only partially successful, but when combined with that of Johann Kepler and others provided Isaac Newton the key elements with which to transform physics. Galileo himself was claimed by modern science as martyr, hero, and exemplar.