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.