Celestial mechanics planetary positions, using geometrical or arithmetical techniques, and contemporary discussions of the physical causes of the planets' motion. Johannes Kepler (1571–1630) was the first to closely integrate the predictive geometrical astronomy, which had been dominant from Ptolemy in the 2nd century to Copernicus, with physical concepts to produce a "New Astronomy, Based upon Causes, or Celestial Physics" in 1609. His work led to the modern laws of planetary orbits, which he developed using his physical principles and the planetary observations made by Tycho Brahe. Kepler's model greatly improved the accuracy of predictions of planetary motion, years before Isaac Newton developed
Phil Nicholson Phil Nicholson Philip D. Nicholson (born 1951) is an Australian-born professor of astronomy at Cornell University in the Astronomy department specialising in Planetary Sciences. He has been editor-in-chief of the journal "Icarus" since 1998. Nicholson received his Ph.D. from Caltech in 1979. Nicholson's research centers on two main areas: orbital dynamics in planetary ring systems and infrared observational studies of planets, their satellites, and their rings. His work has included studies of the ring systems of Saturn, Uranus, and Neptune via Voyager observations and ground-based stellar occultations; Earth-based observations with the 5-meter Hale telescope at Palomar Observatory of several small