Rain and Thunder

This is the sound of thunder and a steady rain hitting against the wet ground with the leaves rustling in the background. The rolling and gradually dissipating rumble of thunder is caused by the time delay of sound coming from different portions of a long stroke of lightning. Because the electrostatic discharge of terrestrial lightning superheats the air to plasma temperatures along the length of the discharge channel in a short duration, kinetic theory dictates gaseous molecules undergo a rapid increase in pressure and thus expand outward from the lightning creating a shock wave audible as thunder. Since the sound waves propagate not from a single point source but along the length of the lightning's path, the sound origin's varying distances from the observer can generate a rolling or rumbling effect.