I confess I’m not as knowledgeable on the works of Carl Sagan as I’d like to be, but it is the 10th anniversary of his passing, and there is a blog-a-thon going on.
Carl Sagan (1934-1996) was a Cornell astronomy professor from right here in Ithaca. His thoughts are some of the most revolutionary of the 20th century, including the books Cosmos and Pale Blue Dot (both of which I know by reputation, but will only finally read in the coming month). Most significantly, in my mind, is his use of the image of Earth from the edge of the solar system, which is partially attributed to starting the modern environmental movement.
Simply put, he helped us as humans rethink our place in the Universe.
Added contribution, courtesy of Ivy Privy (a more recent image):