Galileo learned how to make his first telescope from an article by Hans Lipperhey, a Dutchman who applied for a patent on a the spyglass. Yet Galileo is often called the father of modern astronomy because his ideas had such an impact on the natural sciences, religion, and philosophy.
Not only the ancient Greeks, but also medieval Christians, believed that the earth was subject to corruption and change but that the stars and other heavenly bodies were immutable and perfect. Galileo's observations disproved that theory and gave credence to the Copernican view of the universe, that is, that the earth revolves around the sun rather than vice versa. Galileo also discovered that Jupiter has moons like our own, and that our moon has mountains and valleys rather than being a perfect sphere with mere patterns of light and dark.
In an article for the Telegraph, Professors Paolo Galluzzi of Utrecht University in Holland and Albert van Helden of Rice University in Texas explore how Galileo's discoveries and theories ignited a debate that energized the scholars and clergy of the day, and which eventually caused educated people to see the universe in a new way. The article also chronicles Galileo's early work to improve the clarity and magnification of the telescope from Lipperhey's original design.