All of these effects, although unrelated in most ways, led to the concept of a "barrier" making it difficult for an aircraft to exceed the speed of sound. Erroneous news reports caused most people to envision the sound barrier as a physical "wall", which supersonic aircraft needed to "break" with a sharp needle nose on the front of the fuselage. Rocketry and artillery experts' products routinely exceeded Mach 1, but aircraft designers and aerodynamic engineers during and after World War II discussed Mach 0.7 as a limit dangerous to exceed.