Nicolaus Copernicus is best known for being the father of what would later become humans' modern understanding of the solar system. Prior to this determination, scientists believed that all the objects in the solar system orbited around the Earth itself.
Fortunately for modern astronomers, Copernicus possessed the strength of character necessary to endure the maelstrom that followed his announcement. Until then, it was standard thinking in the West culture, as well as a part of religious dogma, that God had set all things in motion in the manner outlined by Ptolemy. By contradicting Ptolemy's description of how the solar system functioned, Copernicus also contradicted the sincerely held beliefs of the Church and its adherents. He would later be excommunicated by the Church as a heretic, and many who took up his call would follow the same path. It would not be until much later, with Galileo's refinement of the telescope, that concrete evidence would be discovered. Even so, Galileo himself was placed on trial for heresy, found guilty, forced to recant and spent the rest of his life under house arrest. Then referred to as heliocentrism, Copernicus' theory is now widely regarded as one of the most ground-breaking discoveries of his time.