TITLE: On the dynamics near the Lagrangian points of the real Earth-Moon system AUTHORS: Angel Jorba, Enric Castella Departament de Matematica Aplicada i Analisi, Universitat de Barcelona, Gran Via 585, 08007 Barcelona, Spain E-mail: angel@maia.ub.es ABSTRACT: In this work we consider the motion of an infinitessimal particle near the equilateral points of the real Earth-Moon system. We use, as real system, the one provided by the JPL ephemeris: the ephemeris give the positions of the main bodies of the solar system (Earth, Moon, Sun and planets) so it is not difficult to write the vectorfield for the motion of a small particle under the attraction of those bodies. Numerical integrations of this vectorfield show that trajectories with initial conditions in a vicinity of the equilateral points escape after a short time. On the other hand, it is known that the Restricted Three Body Problem is not a good model for this problem, since it predicts a quite large region of practical stability. For this reason, we will discuss a intermediate model that tries to account for the effect of the Sun. This model has some families of lower dimensional tori, that gives rise to a region of effective stablity at some distance of the triangular points. It is remarkable that this region seem to persist in the real system, at least for time spans of 1000 years. This is a summary of the talk presented at the V Jornadas de Mecanica Celeste, Albarracin, Teruel (Spain), June 19-21, 2002.