The heliocentric theory, which states that the Earth revolves around the Sun, was not devised by a single person. It was a gradual process that developed over centuries with contributions from many individuals.

Here are some of the key figures:

* Aristarchus of Samos (c. 310 – c. 230 BC): He was the first Greek philosopher to propose a heliocentric model of the universe, though his ideas were largely ignored at the time.

* Nicolaus Copernicus (1473-1543): He is considered the father of modern heliocentric theory. His book *De Revolutionibus Orbium Coelestium* (On the Revolutions of the Heavenly Spheres) presented detailed calculations and observations that supported a heliocentric model.

* Galileo Galilei (1564-1642): He provided further evidence for the heliocentric theory through his observations with a telescope. He observed the phases of Venus, which could only be explained if Venus orbited the Sun.

* Johannes Kepler (1571-1630): He developed the laws of planetary motion, which explained the elliptical orbits of planets around the Sun.

Therefore, while Copernicus is often credited with the heliocentric theory, it is important to remember that his work built upon previous ideas and was further developed by other astronomers.