While it's often said that Nicolaus Copernicus was the first to discover that planets go around the sun, it's more accurate to say that he was the first to propose a heliocentric model of the solar system.

Here's why:

* Ancient Greek Astronomers: The idea of a heliocentric model wasn't entirely new. Ancient Greek thinkers like Aristarchus of Samos (circa 310-230 BC) had proposed the sun as the center of the universe, but their ideas were not widely accepted.

* Copernicus's Contribution: Copernicus's *De Revolutionibus Orbium Coelestium* (On the Revolutions of the Heavenly Spheres), published in 1543, provided a detailed mathematical model for a heliocentric system. This model explained the observed motions of planets more accurately than the prevailing geocentric model (Earth-centered) that was based on Ptolemy's work.

Therefore, while Copernicus wasn't the first to conceive of the idea, his detailed and well-argued model was pivotal in shifting the scientific understanding of the solar system.