"I've loved the stars too fondly to be fearful of the night" -Galileo Galilei
Contrary to what you may have been taught, he did not invent the telescope. By 1609, relatively weak telescopes had begun to trickle across Europe. Many claimed credit for the invention and none rightly know who first stuck a couple of lenses in a tube and turned it skyward.
It is a matter of some controversy, as laid out in the popular history Stargazer: The Life & Times of the Telescope. The claimants to the title range from an early British surveyor Leonard Digges & Son (who failed to capitalize on their invention if indeed they ever built one) and Hans Lipperhay who has the advantage of being among the first to file for a patent (which was denied, according to Stargazer because even then his was not the only telescope knocking around).
All the same, we honor Galileo's telescope today largely because of the man who built it and how he put it to use. It is noteworthy that when Galileo sat down to make his telescope, it was apparently an artifact of which had had only heard descriptions: Two lenses in a tube that can view far away objects as though they were close-by. With his native intellect and knowledge of optics, the Pisan scholar assembled his telescope as a variable-focus instrument and presented it before the senators.
It was not long before astronomers everywhere were pointing their lenses skyward. It began before Galileo even built his famed stargazer, but as we know it was Galileo overtook the pack and who eventually led the way. His observations of the surface of the moon, that other celestial bodies also had satellites and that the sun has a bad complexion forced a reassessment of the received knowledge of the ancients. The moon was - at the time - supposed to be smooth and perfect. The Medician Moons of Jupiter were a shock, for it proved that not all bodies orbited the Earth. Sunspots marred the perfection of old Sol... the Ptolemaic model of our universe was crumbling.
Paired with the precise measurement of the heavens taken by Tycho Brahe (without a telescope, incidentally) it was readily apparent to all observers that the planets did not move in neat concentric rings. And Earth could not possibly be the center of their oblong orbits. The movement of the Earth itself was the only explanation for the aberrations, the movement of Earth around the sun.
"The scriptures tell us how to go to heaven, not how the heavens go." -Galileo Galilei (attr.)The vastness of space opened before us, a universe that went about its business with little regard for humans.
In the end it was not the position that the Earth held in the universe that brought the full weight of church and state down upon Galileo, it was the position of man in that vastness that doomed his research. The orthodox view held that mankind was the center of God's plan and a vast stretch of infinity filled with planets and stars moving of their own accord did not fit into that equation.
We all know what happened next. In a familiar pattern, the dispute became a matter of politics more than faith and Galileo had made few friends among his peers that would risk all to stand at his side. His views ran afoul of the counter-reformation, a movement fighting to keep Mother Church united against the forces unleashed by Martin Luther and those who came after him.
Galileo's views could not be tolerated and he came into the sights of the Inquisition.
In such a climate, even his powerful patrons among the d'Medici could no longer protect him. It was all they could do to keep him alive. The orthodox viewpoint brooks no rivals and Galileo was forced to recant his position and abandon his research to live the rest of his life in obscurity.
It was a low point for both church and state, an orthodox viewpoint scrambling to keep enough fingers in the dam to hold back the waters of the coming enlightenment. Coffee houses soon replaced the taverns and the minds of men, awakened from the (quite literal) drunken stupor* of the previous age were not eager to return to a time when the darkness drove them indoors. The whole of creation had shifted ever so slightly and humanity was scrambling to keep up, to find its place in a universe where mankind was a part of the plan, not necessarily at its center. The telescope was out of the bag and those whose eyes were turned Earthward could not darken the lenses turned toward the sky.
“I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use." -Galileo GalileiFurther reading: Galileo's Daughter by Dava Sobel
Stargazer: The Life & Times of the Telescope by Fred Watson
The Galileo Project online at Rice University