ix Fully aware of the work accomplished by Mgr. Lemattre, His Majesty King Baudouin enhanced this occasion by placing it under His High Patronage. His Holiness the Pope Jean-Paul II accepted to testify his paternel solicitude for the work of the scientists participating in the symposium. The President of the pontifical Academy of Sciences and the Director of the Vatican Observatory transmitted their fervent wishes for the full success of the symposium. Numerous other eminent people graced the ceremony with their patronage. The academic opening, the addresses of which are pub*lished by the Revue des Questions Scientifiques de Bruxelles , was presided over by Mgr. E. Massaux, Rector of the Catholic University of Louvain who spoke about Lemattre, the University professor. Professor Ch. de Duve, Nobel Prize winner in Medicine, called to mind the role of Lemattre as President of the Pontifical Academy of Sciences; the Emeritus Professor O. Godart, founder of the Institute, recalled the life and work of Mgr. Lemattre; Professor A. Deprit, Senior Mathematician at the National Bureau of Standards, spoke about Lemattre' s work in celestial mechanics and his keen interest for computers; Professor J. Peebles, Professor of Physics at Princeton University, summarized the fundamental contributions of Lemattre to modern cosmology. The attendance of more than three hundred people was enhanced by the presence of Mgr. A. Pedroni, Papal Nuncio, Mr Ph. Maystadt, Minister of Research Policy, Mr E. Knoops, Secretary of State, Mr Y. de Wasseige, Senator, Professor E.
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 Stormer 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.