Galileo Galilei is arguably one of the most important astronomers in human history. Credited by Stephen Hawking as the "single most important person in the birth of modern science", he is remembered as the father of observable astronomy and modern physics. In a time of pervasive geocentric thought, Galileo, having developed the most advanced and far reaching telescope of his time, discovered something amazing in the starry sky. He discovered the four observable moons that orbit Jupiter.
Why is this important? Well, because the dominantly accepted theory of Aristotelian cosmology posited that all heavenly bodies revolve around the Earth. And why shouldn't they? God obviously made the universe for man (and that's "man" as in male not man as in mankind, obviously), didn't he? We are the heroes of the galaxies, the stars of our own intergalactic drama. Right?
What Galileo proved with physical evidence and reasoned logic was the Copernican theory that the Sun, not the Earth, was the center of our solar system. Carl Sagan called this the beginning of the "Great Demotion." By the way, Copernicus was so afraid of being killed by religious zealots that he waited until he was on his deathbed to publish his ideas. Standing on the very shoulders of Galileo (and Copernicus) we now rightly understand our humble place in the vast universe. Not only is the Earth non-central to our solar system, our solar system is non-central to our galaxy (we reside in a rather unremarkable spiral arm). Even more humbling is the fact that our mediocre galaxy is one of a hundred billion more or less just like it. This doesn't disprove the god hypothesis at all. But it does make one wonder what the purpose was in creating the unfathomably immense universe for such a remarkably boring planetary system. Either way, this is important information verified by observable reality. Perhaps it is humbling to swallow. But as the beautiful Flannery O'Connor was fond of saying, "The truth does not change according to our ability to stomach it."
What most people do not realize about Galileo and his unquestioningly true observations is that the Catholic Inquisition actually put him on trial for heresy demanding that he cease advocating and teaching Copernican astronomy. Galileo was threatened to be thrown into a dungeon and tortured by the Church unless he RECANTED. Giordano Bruno, a fellow heliocentrist, had been burned alive for such charges in 1600. Knowing that the truth was inescapable, Galileo recanted and spent the rest of his life in house arrest.
It has been suggested to me that the Christian church is worthy of regarding as true because it has "survived scrutiny" for the last two thousand years. Given the tragic story above it is hard to take seriously anyone who believes that burning people at the stake for dissent qualifies as "surviving scrutiny." It is the most repugnant form of bullying to threaten the life of someone for their ideas and, by my lights, a great testament to the intellectual sham of religious epistemology. Oh but we shouldn't be too hard on the church should we? After all, they did apologize for mistakenly persecuting Galileo nearly FOUR HUNDRED YEARS later.
What mindless, shameful stupidity.
Another important development of Galileo was that in the absence of friction bodies fall to the ground with uniform acceleration. Below is a video of the Apollo 15, the fourth mission to land on the moon. In this video, commander David Scott demonstrates Galileo's three hundred year old prediction. See for yourself the physical evidence of observable reality. Consider for a few moments the immense track record science has of building models that are constantly verified by evidence. Science works.
Think of the world changing ingenuity that made a home in Galileo's mind. And then remember the church with plugged ears threatening this man with torture. Burning and banning his books. And sentencing him to permanent house arrest. If ever there was righteous anger, you should feel it now.