The system of astronomy that was proposed by Nicolaus Copernicus in his book De revolutionibus orbium coelestium, which was published in the month of his death and first seen by him on his deathbed. It used some elements of Ptolemaic astronomy, but rejected the notion, then current, that the earth was a stationary body at the centre of the universe. Instead, Copernicus proposed the apparently unlikely concept that the sun was at the centre of the universe and that the earth was hurtling through space in a circular orbit about it. Galileo’s attempts, some 70 years later, to convince the Catholic church that in spite of scriptural authority to the contrary, the Copernican system was correct, resulted in De revolutionibus being placed on the Index of forbidden books, where it remained until 1835.