Which scientist was the first to propose a heliocentric model of the universe?

The first scientist to propose a heliocentric model of the universe was Nicolaus Copernicus. In his work "De revolutionibus orbium coelestium" published in 1543, Copernicus presented the revolutionary idea that the Sun, rather than the Earth, is at the center of the universe. This marked a significant shift from the previously accepted geocentric model, which placed the Earth at the center. Copernicus's model posited that the Earth and other planets orbit the Sun, a concept that laid the groundwork for modern astronomy. His ideas challenged long-held beliefs and ultimately paved the way for future astronomers, such as Galileo and Kepler, to build upon and refine our understanding of celestial mechanics.