Copernicus, or Nicolaus Copernicus, was a Renaissance astronomer from Poland who formulated the heliocentric model of the universe, which posited that the Earth and other planets revolve around the Sun. His seminal work, "De revolutionibus orbium coelestium," published in 1543, challenged the long-held geocentric view that placed the Earth at the center of the universe. Copernicus' ideas laid the groundwork for modern astronomy and significantly influenced the Scientific Revolution.