'N. Copernicus', (late 18th early 19th century). Portrait of Polish astronomer Nicolaus Copernicus (1473-1543), considered to be the father of modern astronomy and founder of heliocentric cosmology. Prior to the work of Copernicus, the Earth was believed to be the stationary centre of the universe, a notion first advocated by the Egyptian astronomer Ptolemy. His pioneering work "The Revolutions of Celestial Spheres", 1543, describes his idea of a Sun-centred universe, in which the Earth is merely one of the planets revolving around the Sun and rotating on its axis.