Entropy and Time

Since the 19th century, time and entropy have come together. In particular, entropy was found to be the key of the so-called “arrow of time” — the distinction between the past and future directions of time is given by the direction in which entropy increases in isolated systems. The link between both concepts has given place to abundant literature and discussion, and opened new and fundamental problems. In this chapter, we address the puzzling relation between entropy and time in its different facets. The main aim is to get some clarity on the relation and its underlying assumptions