Happy Birthday, Nicolaus
Born today in 1473, the originator of the theory which bears his name - the Copernican, or heliocentric, system, which challenged and then (for most people) replaced the geocentric system, which held that the earth was the center and everything revolves around it. Nicolaus Copernicus was a brilliant polymath who merely dabbled in astronomy, and yet he removed the geocentered (and anthrocentered) universe from the realm of science.
He died in 1543, apparently, of a stroke, and legend has it that he regained consciousness in time for the first printed copy of his, if you'll pardon the pun, revolutionary work De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres) to be placed into his hands, allowing him to see his life's work before he died. It's only a legend, but it's a nice one, isn't it?
(painting by Jan Matejko, displayed in the Nicholaus Copernicus Museum in Frombork)
And let's not forget to teach the controversy! Ha