Kepler's concept of an attractive force from the Sun - a virtue, early 16th century. His idea of 'gravity' by which he hoped to account for his elliptical planetary orbits. Planets, moons and stars were rotating magnets and their magnetism maintained planet orbits with forcefield-thread vortexes acting mechanically. Image from Epitome Astronomiae Copernicanae. Johannes Kepler (1571-1630) was a German mathematician, astronomer and astrologer. A key figure in the 17th century scientific revolution, he is best known for his laws of planetary motion based on his works Astronomia nova, Harmonices Mundi, Epitome Astronomiae Copernicanae. These works also provided one of the foundations for Isaac Newton's theory of universal gravitation.