A sudden, violent disturbance in a medium, here heating gas to emit light.A shock wave is a sudden, violent disturbance that travels through a medium — air, water, plasma, or even solid material — faster than the speed of sound in that medium. Unlike an ordinary sound wave, which compresses and expands the medium gently, a shock wave is a sharp, nearly discontinuous jump in pressure, temperature, and density. When it passes through a gas, it can heat the gas so intensely that it emits light, which is why meteor fireballs, supernova remnants, and re-entering spacecraft glow so brightly.
The concept was developed in the mid-19th century, with significant contributions by Ernst Mach in the 1870s, who studied supersonic projectiles and photographed shock waves using schlieren imaging.
A shock wave forms when something pushes a medium faster than the medium can carry away the disturbance as a normal sound wave. The leading edge of the disturbance outruns the sound waves ahead of it, piling up into a steep front. Across this front, the medium's properties change abruptly: pressure, temperature, and density jump upward, while the flow velocity drops. The energy of the motion is converted into heat, and in gases this heat can be high enough to ionize atoms and produce visible light.
Shock waves are used in medicine for lithotripsy (breaking kidney stones), in industry for explosive forming of metals, and in astrophysics to explain the heating of stellar coronae and the acceleration of cosmic rays.
The crack of a bullwhip is a small shock wave created by the tip moving faster than the speed of sound.









