  It is a remarkable fact that all processes occurring in the observable
Universe are irreversible, whereas the equations through which the fundamental
laws of physics are formulated are invariant under time reversal. The emergence
of irreversibility from the fundamental laws has been a topic of consideration
by physicists, astronomers and philosophers since Boltzmann's formulation of
his famous "H" theorem. In this paper we shall discuss some aspects of this
problem and its connection with the dynamics of space-time, within the
framework of modern cosmology. We conclude that the existence of cosmological
horizons allows a coupling of the global state of the Universe with the local
events determined through electromagnetic processes.
