an imaginary line through the center of a planet around which the planet rotates axis of rotation the time it takes for a planet to rotate once around its rotational axis period of rotation the time it takes a planet to move completely around the around the Sun period of revolution an oval ellipse the average distance from Earth to the Sun astronomical unit an object that revolves around a planet satellite different appearance of the Moon as it orbits Earth lunar phase a total or partial obscuring of one celestial body by another eclipse
Of Mice and Men 