Galileo Galilei died on this day in 1642. His work revealing that the earth orbits the sun, not the other way around, launched an astronomical revolution. (Get it?) Among astronomers, there was a lively debate on whether the universe was geocentric or heliocentric, but the vast majority of people (including the Catholic Church) firmly believed in the former and abhorred the latter. Galileo's work was recognized as important, even by those who disagreed with him, and it was a turning point in modern science that allowed us to do things like, you know, go to the moon. Despite making such a crucial discovery, Galileo's uncompromising view on heliocentrism was also what destroyed his life.
According to the Roman Inquisition, a kind of religious judicial system charged with determining whether someone had committed heresy (a verdict they handed out with great frequency), Galileo's observations directly contradicted part of the Bible and were facially "foolish and absurd," and he was forced to recant his views in 1616.
Luckily, seven years later a friend of his ended up as Pope Urban VIII, who encouraged the astronomer to keep writing on the issue so long as he didn't explicitly argue that planets revolved around the sun. Unfortunately, Galileo showed his hand a little too much in his writings, and the pope dropped him like a hot potato. After another trial in 1633, the scientist was put under house arrest and his works banned; he died nine years later.
This was, of course, a very simplified version of the tale. For more detail, including some myth-busting of the conventional wisdom on Galileo's trial, read this article from the University of California, Los Angeles.
