Indeed, if in the above case [i.e. starting in a state where one particle is moving, and all the others lie still on the bottom], after a time τ which is long enough to obtain the stationary state, one suddenly assumes that the velocities of all atoms are reversed, we would obtain an initial state that would appear to have the same character as the stationary state. For a fairly long time this would be appropriate, but gradually the stationary state would deteriorate, and after passage of the time τ we would inevitably return to our original state: only one atom has absorbed all kinetic energy of the system […], while all other molecules lie still on the bottom of the container.