Abstract
Some processes happen spontaneously. What, at a macroscopic level, appears as a nature’s tendency, is an effect of the complex statistical behaviour of the microscopic particles: their overall net effect emerges at the macroscopic level as a spontaneous force that determines if and how a system can spontaneously change, and if and toward which direction a process is therefore started.
Keywords: Canonical ensemble, Canonical partition function, Crossproduct, Momentum partition function, Phase space, Positional partition function, System configuration, Tendency.