3. Astroparticle Physics (CSN2)

Extended interpretation of Keplerian Laws

by Giuseppina Modestino (Istituto Nazionale di Fisica Nucleare)

Aula Seminari (LNF INFN)

Aula Seminari



The Keplerian parameters of an orbit of a two-body system are obtained from basic considerations of kinematics and Newtonian mechanics. The fundamental physical properties of a system come to light naturally by considering the geometric parameters of the orbits, first of all, geodesics between the two bodies. Following the Kepler’s conception of assigning a crucial role to distance measurements, and introducing a metric in agreement with the speed of light c, we discover correspondences between physical and geometric parameters of the orbits of the planets. It turns out that the eccentricity of the elliptical orbit corresponds to the total momentum of the system, and the precession angle represents the scattering angle of one of the bodies with respect to the direction of the momentum. Formulating the gravitational potential with the elliptic parameters, an expression analogous to retarded Lienard-Wiechert potential is obtained.