How far from equilibrium is active matter ?
Active Matter in 2016 encompasses such a broad range of systems that it is almost a challenge to define what’s behind this terminology. One of the unifying characteristics to all active systems is that individual constituents convert an external continuous supply of energy into random motion. On a representative model of an active system, we will explain how, by looking at the movie of its time evolution, one can tell whether, and how far, the system lies away from equilibrium. We will also provide a microscopics based explanation of some of the macroscopic effects that are specific to active particle systems.