In 1543, Copernicus' idea that the Sun was the center of the solar system changed everything.

http://starchild.gsfc.nasa.gov/docs/StarChild/whos_who_level2/copernicus.html
Nicolaus Copernicus died more than 450 years ago but is still considered the founder of modern astronomy!

http://www.tau.ac.il/~museum/galileo/heliocentric.html
The Copernican Model of the Planetary System