Simple simulation of solar system

The article presents a simple derivation of a set of approximate formulas f or the rate of change of orbital elements of a planet, perturbed by a time- averaged gravitational farce due to the remaining planets of the solar syst em. The corresponding set of differential equations for long-time developme nt of planetary orbits is then numerically integrated and the results are s hown to be consistent with Milankovitch theory of climatic cycles.