Who proposed the heliocentric theory?

The heliocentric theory, which posits that the Earth and other planets revolve around the Sun, was proposed by Nicolaus Copernicus. His significant work, "De revolutionibus orbium coelestium" (On the Revolutions of the Celestial Spheres), published in 1543, laid the foundation for modern astronomy and marked a pivotal shift away from the geocentric model that placed the Earth at the center of the universe.

This theory was groundbreaking as it challenged the long-held belief, supported by Ptolemaic models, that the Earth was the center of the universe. Copernicus's model provided a more straightforward explanation for the observed movements of celestial bodies, ultimately leading to a revolution in scientific thought during the Renaissance. His ideas paved the way for later astronomers, including Galileo Galilei, who supported the heliocentric view through his observations, but the original proposal belongs to Copernicus.