Does the second law hold at cosmic scales?
  The second law of thermodynamics is known to hold at small scales also when
gravity plays a leading role, as in the case of black holes and
self-gravitating radiation spheres. It has been suggested that it should as
well at large scales. Here, by a purely kinematic analysis \textemdash based on
the history of the Hubble factor and independent of any cosmological model
\textemdash , we explore if this law is fulfilled in the case of homogeneous
and isotropic universes regardless of the sign of the spatial curvature.
