The lightning is extremely hot and during that brief time the air is superheated and expands violently. The air then cools quickly. An everyday example of a vibration in the air that produces a bang is when a balloon is filled with air until it pops. read more
The lightning. The speed of light is faster than the speed of sound. In addition, lightning creates thunder, therefore it happens first, therefore must be faster. See the related link for more information. read more
This makes the sound travel in all different directions. The further away the source of the sound is, the more the sound gets distorted. Therefore, when you hear rumbling thunder, the lightning bolt was far away. When you hear a crack or boom of thunder, the lightning bolt is close to you (100 m). read more