Entropy Revisited: the Plausible Role of Gravitation

We first present open questions related to the foundations of thermodynamics and statistical physics. We then argue that in principle one can not have "closed systems", and that a universal background should exist. We propose that the gravitational field plays this role, due to its vanishing energy-momentum tensor. This leads to a new possible picture, in which entropy and irreversibility in macroscopic systems emerge from their coupling to the background gravitational field.