  This paper is intended to clarify some of the rather well-known aerodynamic
phenomena. It is also intended to pique the interest of the layman as well as
the professional. All aerodynamic forces on a surface are caused by collisions
of fluid particles with the surface. While the standard approach to fluid
dynamics, which is founded on the fluid approximation, is effective in
providing a means of calculating various behavior and properties, it begs the
question of causality. The determination of the causes of many of the most
important aerodynamic effects requires a microscopic examination of the fluid
and of the surface with which it interacts. The Kutta-Joukowski theorem is
investigated from first physical principles. It is noted that the circulation
does not arise alone as a physical phenomenon, e.g. air doesn't flow forward
under a wing, but must be added to the translation flow. The circulation term
is necessary to take into account the vertical deflection of the air flow by a
wing. Various aerodynamic devices are discussed, e.g. rocket engine exhaust
diffuser and the perfume atomizer. The section on slurries discusses
pyroclastic flow as occurs in violent volcanic eruptions.
