In attempting to clarify Ptolemy’s explanation of the universe Copernicus realised that the Sun was at the centre and that the Earth and the other planets revolved around it. He also realised that the Earth rotated once a day to give us day and night.

As he worked on the fine details his new system became as complicated as Ptolemy’s. Worried about appearing a fool, Copernicus spent most of his life working on his theory before publishing “The Book of Revolutions of the Heavenly Spheres” in the year he died.