The physical mechanisms enacting the direction of time remain one of the most guarded secrets of nature. In this presentation we try to look into these secrets and explore the hypothesis that the perceived direction of time has thermodynamic origins. Over the years, this hypothesis was advocated by a number of prominent scientists (e.g. Boltzmann, Hawking) but is still not widely known. There are two reasons behind this. First, overwhelming majority of people (including most physicists) tend to implicitly accept “the natural flow of time” based on common intuition as a working model. Second, accepting one hypothesis or the other does not seem to have any practical implications --- nether of the assumptions is seen to produce a testable physical theory capable of discriminating these assumptions. So far, consistent investigation of the nature of time has been largely confined to the domain of philosophy, where numerous attempts to build a logical scheme around our intuitive perception of time have faced mounting difficulties.

It appears, however, that Boltzmann’s time hypothesis does have physical implications and does raise important questions. If this hypothesis is accepted, thermodynamics can have two possible versions with respect to matter/antimatter duality --- symmetric (CP-invariant) and antisymmetric (CPT-invariant). These versions are mutually incompatible and only one of them can be real. The choice between these versions can be tested experimentally, although this is not a simple matter, even at the present level of technology. In this presentation we will discuss the direction of time and explore implications of these versions of thermodynamics.