What do a supernova explosion in outer space, flow around an airfoil
and knocking in combustion engines have in common? The physical
and chemical mechanisms as well as the sizes of these processes are quite
different. So are the motivations for studying them scientifically. The
supernova is a thermo-nuclear explosion on a scale of 108cm. Astrophysicists try
to understand them in order to get insight into fundamental properties of
the universe. In flows around airfoils of commercial airliners at the scale of
103cm shock waves occur that influence the stability of the wings as well as
fuel consumption in flight. This requires appropriate design of the shape and
structure of airfoils by engineers. Knocking occurs in combustion, a chemical
process, and must be avoided since it damages motors. The scale is 101 cm and
these processes must be optimized for efficiency and environmental
considerations. The common thread is that the underlying fluid flows may at a certain
scale of observation be described by basically the same type of hyperbolic
systems of partial differential equations in divergence form, called conservation
laws. Astrophysicists, engineers and mathematicians share a common interest
in scientific progress on theory for these equations and the development of
computational methods for solutions of the equations.