Astrology and Astronomy - Historical Divergence

Historical Divergence

Astrology and astronomy were indistinguishable for a very long time – the funding from astrology supported some astronomical research, which was in turn used to make more accurate ephemerides for use in astrology. In Medieval Europe the word Astronomia was often used to encompass both disciplines as this included the study of astronomy and astrology jointly and without a real distinction; this was one of the original Seven Liberal Arts. Kings and other rulers generally employed court astrologers to aid them in the decision making in their kingdoms, thereby funding astronomical research. University medical students were taught astrology as it was generally used in medical practice.

Astronomy and astrology diverged over the course of the 17th through 19th centuries. Copernicus didn't practice astrology (nor empirical astronomy; his work was theoretical), but the most important astronomers before Isaac Newton were astrologers by profession – Tycho Brahe, Johannes Kepler, and Galileo Galilei. Newton most likely rejected astrology, however (as did his contemporary Christiaan Huygens), and interest in astrology declined after his era, helped by the increasing popularity of a Cartesian, "mechanistic" cosmology in the Enlightenment.

Also relevant here was the development of better timekeeping instruments, initially for aid in navigation; improved timekeeping made it possible to make more exact astrological predictions—predictions which could be tested, and which consistently proved to be false. By the end of the 18th century, astronomy was one of the major sciences of the Enlightenment model, using the recently codified scientific method, and was altogether distinct from astrology.