Nicolaus Copernicus (1473-1543), Polish astronomer who began the revolution that overthrew more than 1000 years of astronomical thought. Since the time of Ptolemy in the second century AD, the Earth had been considered to be the immovable centre of the universe. From 1512, Copernicus developed a mathematical model for his heliocentric theory, in which the Earth was said to be one of several planets moving around the Sun. Copernicus feared persecution by the Roman Catholic Church, and delayed publication of his book, The Revolution of the Heavenly Spheres, until near his death. He received his copy from the printers on the day he died. The book was banned by the Roman Catholic church from 1616 until 1835. Artwork from Pioneers of Science (Oliver Lodge, 1893).