In the 16th century, Nicolaus Copernicus proposed a major shift in the understanding of the cycle of the heavenly spheres. Driven by a desire for a more perfect (i.e. circular) description of the cosmos than the prevailing Ptolemaic model - which posited that the Sun circled a stationary Earth - Copernicus instead advanced a heliostatic system where a stationary Sun was located near, though not precisely at, the mathematical center of the heavens. In the 20th century, the science historian Thomas Kuhn characterized the "Copernican Revolution" as the first historical example of a paradigm shift in human knowledge,. Both Arthur Koestler and David Wootton, on the other hand, have disagreed with Kuhn about how revolutionary Copernicus' work should be considered.
