  Quel est, ou pourrait \^etre, la topologie globale de la partie spatiale de
l'Univers ? L'Univers entier (pr\'ecis\'ement, l'hypersurface spatiale de
celui-ci) est-il observable ? Les math\'ematiciens, les physiciens et les
cosmologistes observationnels ont des approches diff\'erentes pour aborder ces
questions qui restent ouvertes.
  What is, or could be, the global topology of spatial sections of the
Universe? Is the entire Universe (spatial hypersurface thereof) observable ?
Mathematicians, physicists and observational cosmologists have different
strategies to approaching these questions which are not yet fully answered.
