Mikołaj Kopernik, known as Nicolaus Copernicus in Latin, was a Polish mathematician and astronomer born on February 19, 1473. He is best known for formulating the heliocentric theory, which proposed that the Sun is at the center of the universe, rather than the Earth. This revolutionary idea challenged the long-held geocentric model that placed the Earth at the center. Kopernik's major work, titled De revolutionibus orbium coelestium, was published in 1543, shortly before his death. His theories laid the groundwork for modern astronomy and influenced later scientists, including Galileo Galilei and Johannes Kepler. Kopernik's contributions marked a significant shift in our understanding of the cosmos.