thunder

Why does thunder rumble? When a lightning bolt flashes through the sky we see it instantly. Thunder takes a few seconds longer to reach us. Sound travels about a mile in 5 seconds. Start counting when you hear a lightning flash. If you hear the thunder in 5 seconds, the lightning's a mile away; in 10 seconds and it is two miles away. We hear rumbling as sound from other parts of the flash hits our ears. Thunder from the part of flash nearest us reaches our ears first. The phenomenon of "rolling thunder" is many lightning flashes and their sounds occurring in sequence. Thunder is the explosive sound produced by an ordinary lightning discharge. The lightning bolt quickly heats the air around it to such a high temperature that air molecules are pushed apart with tremendous force, producing a sound wave. Thunder lasts much longer than lightning and changes in pitch and loudness. This happens for several reasons: the lightning bolt has an irregular shape, the air expands in all di rections at once, lightning bolts overlap, and objects on the ground interfere with the sound. Thunder is heard after lightning is seen because sound travels more slowly than light.