While the idea of a heliocentric solar system (sun-centered) existed in ancient Greece, it was Nicolaus Copernicus who is credited with the modern theory of heliocentrism.

Here's why:

* Copernicus's book "De Revolutionibus Orbium Coelestium" (On the Revolutions of the Heavenly Spheres), published in 1543, was the first detailed and comprehensive model of a heliocentric solar system.

* He provided mathematical and observational evidence to support his theory, challenging the prevailing geocentric model (Earth-centered) that had been accepted for centuries.

* Copernicus's work was revolutionary and laid the foundation for future astronomical discoveries, paving the way for Galileo and Kepler, who further developed and refined the heliocentric model.

While ancient Greek philosophers like Aristarchus of Samos proposed heliocentric ideas, Copernicus's work was the first to be widely accepted by the scientific community, marking a significant shift in our understanding of the universe.