  Recent empirical studies found different thermodynamic phases for collective
motion in animals. However, such a thermodynamic description for human movement
remains unclear, mainly due to the limited resolution of existing tracking
technologies. In this Letter, we used a new ultra-wideband radio frequency
identification technology to collect high-resolution spatial-temporal data for
classroom movements. We measured the effective temperatures for the underlying
systems, and found two social phases, gas and liquid-vapor coexistence,
associated with different temperatures. We also proposed a simple statistical
physics model that can reproduce different empirically observed phases.
