how do clouds thunder?
Answers
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 formed by the intense heating produced by lightning. The thunder you hear is made up of vibrations that travel as sound waves through the air until they reach your ear.
When lightning occurs, a large discharge of electricity causes the surrounding air to vibrate as it passes through the atmosphere to the surface.
When air molecules experience an increase in temperature, they expand. The faster these air molecules heat up, the faster they expand.
In the case of lightning, the surrounding air is being heated to temperatures hotter than the surface of the sun, in a fraction of a second. This expansion of air occurs so rapidly that it begins to forcefully push the surrounding air particles, creating more vibrations and compressing the air in front of it.
As the air begins to cool, it rapidly contracts, which creates the initial cracking sound of thunder. This air column continues to vibrate, forming sound waves that make up the rumbling sounds of thunder.
Since the speed of light travels faster than the speed of sound, we see lightning before we hear the thunder it’s producing. If you see lightning bolts and then an immediate crack of thunder, that means the lightning struck close by.