In Search of an Explanation for the Thermodynamical Arrow of Time in Cosmology

The theory of thermodynamics displays an asymmetry in time, associated with the increase of entropy described by the Second Law. In 1866 Boltzmann set of on the ambitious quest to deduce the Second Law from the dynamics underlying thermodynamic processes. In itself this was a problematic enterprise, because the underlying dynamics are symmetric in time. When Boltzmann died in 1905, this problem with the Thermodynamical Arrow of Time remained unsolved.

About 50 years later the problem regained attention, when it was picked up by Reichenbach and Gold. Various attempts to solve the problem have been made since, most of them in some way related to contemporary cosmology. Specifically, these are: the Anthropic Argument, the Past Hypothesis and several versions in which the Cosmological Arrow of Time (the expansion of the universe) plays a dominant role. In have researched whether one of these attempts has lead to a solution of Boltzmann's problem.

The topic of this presentation is an overview of these attempts. I will argue that none of the attempted schemes provides a satisfactory solution. However, I believe there are some valuable pieces within these schemes. I will put these pieces together and argue that the resulting puzzle provides a satisfactory solution to the problem with the Thermodynamic Arrow of Time.