I Cosmology -- Physical and cosmological interactions -- Impact of Lemaitre's ideas on modern cosmology -- Massive neutrinos and photinos in cosmology and galactic astronomy -- The primordial nucleosynthesis -- A generalization of the Lemattre models -- Is the universe homogeneous on a large scale? -- Vacuum inhomogeneous cosmological models -- The significance of Newtonian cosmology -- Numerical simulation of evolution of a multi-dimensional Higgs field in the new inflationary scenario -- Primordial nucleosynthesis and nuclear reaction rates uncertainties -- Time and singularity -- Quasar energy from frozen fusion via massive neutrinos? -- Estimation of galactic masses using the zero energy-momentum cosmological principle -- II - Celestial Mechanics -- Dynamics of orbiting dust under radiation pressure -- Non gravitational forces in the evolution of the solar system -- Generalizations of the restricted problem of three bodies -- Secular perturbations of asteroids with commensurable mean motions -- A mechanism of depletion for the Kirkwood's gaps -- On the stability of the solar system as hierarchical dynamical system -- A relativistic approach to the Kepler problem -- The three-body problem in stellar dynamics -- The critical periodic orbits in the Störmer problem -- A multimode investigation of granular and supergranular motions I: Boussinesq model -- III - Structure of the Universe and Cosmic Rays -- Galaxy formation revisited -- Clusters and superclusters -- Cosmic ray sources and confinement in the galaxy -- Strong evidence for metagalactic shock waves at redshifts z?2-3 -- Algebraic programming in general relativity and cosmology -- Finite euclidean and non-euclidean geometry with applications to the finite pendulum and the polygonal harmonic motion. A first step to finite cosmology -- IV - Georges Lemaitre: The Man and His Work -- Monsignor Georges Lemaitre -- The Scientific Work of Georges Lemaitre -- Bibliography of Georges Lemaitre -- Author Index.