What causes the sound of thunder?

Due to the electric current (which is a form of energy) going through the air from the lightning, the air is heated immensely locally. This causes the air to expand instantaneously which produces a bang. A couple of bangs one after the other is what we call thunder.

Thunder is caused by the rapid expansion of the air surrounding the path of a lightning bolt.

From the clouds to a nearby tree or roof, a lightning bolt takes only a few thousandths of a second to split through the air. The loud thunder that follows the lightning bolt is commonly said to come from the bolt itself. However, the grumbles and growls we hear in thunderstorms actually come from the rapid expansion of the air surrounding the lightning bolt.

As lightning connects to the ground from the clouds, a second stroke of lightning will return from the ground to the clouds, following the same channel as the first strike. The heat from the electricity of this return stroke raises the temperature of the surrounding air to around 27,000 C° (48,632 F°). Since the lightning takes so little time to go from point A to point B, the heated air has no time to expand. The heated air is compressed, raising the air from 10 to 100 times the normal atmospheric pressure. The compressed air explodes outward from the channel, forming a shock wave of compressed particles in every direction. Like an explosion, the rapidly expanding waves of compressed air create a loud, booming burst of noise.

Because electricity follows the shortest route, most lightning bolts are close to vertical. The shock waves nearer to the ground reach your ear first, followed by the crashing of the shock waves from higher up. Vertical lightning is often heard in one long rumble. However, if a lightning bolt is forked, the sounds change. The shock waves from the different forks of lightning bounce off each other, the low hanging clouds, and nearby hills to create a series of lower, continuous grumbles of thunder.

Thunder is caused by the rapid expansion of air due to the heat of lightning. Lightning is created with the friction of updrafts and downdrafts. There can be lightning without thunder, this is known as heat lightning. When there's thunder, there has to be lightning because that's the heat expanding the air which makes the sound of thunder.

SHORT, SIMPLE, EASY TO UNDERSTAND! When lightning flashes, it's soo hot it cuases particles in air to vibrate which makes a noise which you hear as thunder. The reason you see lightnign before thunder is becuase light travels faster than sound which depends on how far away lightnign struck to hear the thunder.

Thunde is caused by the rapid expansion of the air surrounding the path of a lightning bolt. The shock waves nearer to the ground reach your ears first, followed by the crashing of the shock waves from higher up.

This can also be applied to what causes the sound of a spark. Lighting releases a burst full of electrons to ground it. The pathway of the lighting causes a massive temperature increase through its path, causing air to expand very fast. Thus, sound is generated!