Nicolaus Copernicus proposed the heliocentric theory during the Renaissance. His groundbreaking work, "De revolutionibus orbium coelestium," published in 1543, argued that the Sun, rather than the Earth, was at the center of the universe. Copernicus's model challenged the long-held geocentric view promoted by Ptolemy and the Church, which placed the Earth at the center. His ideas laid the foundation for modern astronomy and influenced later scientists, including Galileo and Kepler, ultimately leading to the scientific revolution. Copernicus's shift in perspective encouraged a more empirical approach to science, sparking curiosity and debate that would change humanity's understanding of its place in the cosmos.