Ptolemy had this idea that the universe was geocentric, meaning the earth was at the center of the universe
However, one night, Nicolaus Copernicus thought, What if the Sun was at the center of the universe and not the Earth
Eventually, in 1543 Copernicus' major work 'De Revolutionibus Orbium Coelestium' was published describing how the universe was Heliocentric
Later that year, Copernicus died
However, from Copernicus' book, the world soon began to believe that the universe was heliocentric. That belief has held up throughout history and is still believed today.