Shock wave cannot travel any further upstream and the pressure progressively builds in that region; a high pressure shock wave rapidly forms. Shock waves are not conventional sound waves; a shock wave takes the form of a very sharp change in the gas properties. Shock waves in air are heard as a loud "crack" or "snap" noise. Over longer distances, a shock wave can change from a nonlinear wave into a linear wave, degenerating into a conventional sound wave as it heats the air and loses energy. The sound wave is heard as the familiar "thud" or "thump" of a sonic boom,
Faster-than-light oscillator ticking too fast. In special relativity, it is impossible to accelerate an object the speed of light, or for a massive object to move the speed of light. However, it might be possible for an object to exist which moves faster than light. The hypothetical elementary particles with this property are called tachyonic particles. Attempts to quantize them failed to produce faster-than-light particles, and instead illustrated that their presence leads to an instability. Various theorists have suggested that the neutrino might have a tachyonic nature, while others have disputed the possibility. Mechanical equations to describe hypothetical exotic matter which