Nicolaus Copernicus was the first astronomer to develop a complete theory of the universe with the sun at the center. With his "heliocentric model" published in 1543, Copernicus showed that the motions of celestial bodies could be explained without placing Earth at the center. At that time in ...
Copernicus lived in a time 【2】 people still believed everything moved around the earth in 【3】 universe. But through his years of 【4】 (observe) and mathematical calculations, Copernicus became confused because he found the earth was not the centre of the solar system. He kept improving...