Named in memory of the great French mathematician, astronomer and physicist, Pierre-Simon Marquis de Laplace (1749–1827). Although Newton {see planet  (8000)} had concluded that divine intervention was periodically required to preserve the solar system in equilibrium, Laplace managed to prove in 1773, by applying Newtonian gravitation, the invariability of planetary mean motions to the cubes of the eccentricities and inclinations. In 1786 he showed that the effects of planetary perturbations were conservative and periodic, not cumulative and disruptive; the eccentricities and inclinations of planetary orbits to each other will remain small, constant and self-correcting. In 1796 he published his famous Exposition du système du monde, which treats also his “nebular hypothesis”, which ascribes the origin of the solar system to the contraction of a gaseous nebula. His monumental Traité de mécanique céleste, published between 1798... _ _.