Offering a brief description of Finkelstein's approach to quantum theory and some of its ramifications, this text specifically examines his suggestion that some sort of quantum-set-like structure should underlie our macroscopic perception of spacetime, developing it to the point where a proportion of fundamental physics (for a massless world) may be formally derived from the ground up. In detail, a model of what Finkelstein has called a "quantum net", in conjunction with a single Schwinger-like dynamical principle, gives rise to the standard Langrangians for: massless Dirac fermions; general relativity; and Yang-Mills fields for the gauge groups SU(n), n = 3,4. These Langrangians emerge replete with (Feynman) gauge-fixing terms and ghost fields Structure and basic properties of shock waves in gases; shock wave propagation through a gas; interaction of a plane shock wave with disturbances and stability of shock waves; reflection of a shock wave from a smooth body of an arbitrary shape; reflection of a shock wave from a concave body and shock focusing; propagation of shock waves through a weakly ionized plasma