  We describe a simple framework for teaching the principles that underlie the
dynamical laws of transport: Fick's law of diffusion, Fourier's law of heat
flow, the Newtonian viscosity law, and mass-action laws of chemical kinetics.
In analogy with the way that the maximization of entropy over microstates leads
to the Boltzmann law and predictions about equilibria, maximizing a quantity
that E. T. Jaynes called "Caliber" over all the possible microtrajectories
leads to these dynamical laws. The principle of Maximum Caliber also leads to
dynamical distribution functions which characterize the relative probabilities
of different microtrajectories. A great source of recent interest in
statistical dynamics has resulted from a new generation of single-particle and
single-molecule experiments which make it possible to observe dynamics one
trajectory at a time.
