Astronomers

apogee appear Astronomer Royal astronomy attraction axis calculated called cause celestial sphere centre century circle complete consider Copernik Copernikan system direction discovered discovery diurnal motion eccentricity ecliptic effect ellipse epicycles equal equant equator exactly explained fact fixed stars force acts Galileo greater Halley heavenly bodies hence Herschel Hipparchus inferior planets inversely Jupiter Kepler labours Lagrange Laplace latus rectum law of gravitation laws of motion libration light line joining line of apses M₁ M₂ magnitudes mass mathematical moon moon's motion moon's orbit nearer nearly Newton nodes observed particle passed path perigee perturbing force physical astronomy position produced proportional Ptolemy radius vector reason regress rest result revolution revolve round rotation round the sun satellites Saturn seems seen solar system space spherical straight line supposed syzygy telescope theory tion true Tycho Brahé uniform rate universe Uranus velocity verified vibrations whole