* Ancient Greece: Philosophers like Aristarchus of Samos (c. 310-230 BC) proposed a heliocentric model (Sun-centered) based on observations and logical reasoning. However, this model was not widely accepted.
* Medieval Period: The prevailing model was geocentric (Earth-centered), supported by the Church and influential thinkers like Ptolemy.
* Nicolaus Copernicus (1543): Published "De Revolutionibus Orbium Coelestium" proposing a heliocentric model with mathematical backing. This was still controversial and faced strong opposition.
* Galileo Galilei (early 1600s): Made telescopic observations supporting the heliocentric model (phases of Venus, moons of Jupiter). This led to conflict with the Church.
* Johannes Kepler (early 1600s): Developed laws of planetary motion, mathematically confirming the elliptical orbits of planets around the Sun.
* Isaac Newton (late 1600s): His law of universal gravitation provided a physical explanation for the heliocentric system.
So, it wasn't a single moment of discovery, but a gradual process of observation, mathematical models, and scientific debate over centuries. While Copernicus is often credited with "discovering" it, his work built on earlier ideas and was only one step in a long scientific journey.
