PRIDE CHEKERAKopernik model was later anchored by Kepler's three laws of
planetary mechanics, of which first law was published in
Astronomia Nova in 1609, and the third in Harmonices Mundi
in 1619; they are well known as Kepler's laws. These are:
(1) the orbit of each planet is an ellipse with the Sun at one
of the foci;
(2) the radius vectors of each planet sweeps out equal areas in
equal time,
(3) the squares of the periods of the planets are proportional to
the cubes of their mean distances from the Sun.dθ
v Directrix
F m
Focus r
푚 0 .........θ........................ x
d
Fig 1: Diagrammatic representation of Kepler’s laws of
Planetary motion.