A model of the Universe with the Sun at its centre.
Polish astronomer, Nicolaus Copernicus (1473-1543) advanced the theory that the Earth and other planets revolve around the Sun. This was highly controversial at the time, since the prevailing Ptolemaic model held that the Earth was the centre of the universe, and all objects, including the sun, circle it. The Ptolemaic model had been widely accepted in Europe for 1000 years when Copernicus proposed his model. It should be noted, however, that the heliocentric idea was first put forth by Aristarcus of Samos in the 3rd century B.C., a fact known to Copernicus but long ignored by others prior to him.
"Of all discoveries and opinions, none may have exerted a greater effect on the human spirit than the doctrine of Copernicus."