Why do clouds thunder?

QuestionsCategory: High School PhysicsWhy do clouds thunder?
1 Answers
Profile photo of Big Bang BoffinBig Bang Boffin Moderator answered 3 years ago

Wikipedia gives the following quick description of a thunder:

Thunder is the sound caused by lightning. Depending on the distance and nature of the lightning, thunder can range from a sharp, loud crack to a long, low rumble (brontide). The sudden increase in pressure and temperature from lightning produces rapid expansion of the air surrounding and within a bolt of lightning. In turn, this expansion of air creates a sonic shock wave, similar to a sonic boom, which produces the sound of thunder, often referred to as a clap, crack, peal of thunder, or boom.


Thunder Bolt
Thunder Bolt

Now let’s see what produces the sound(thunder).
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.
Some facts:

  • To judge how close lightning is, count the seconds between the flash and the thunderclap. Each second represents about 300m (984.25ft).
  • Lightning does not always create thunder. In April 1885, five lightning bolts struck the Washington Monument during a thunderstorm, yet no thunder was heard.

Resources:
https://www.loc.gov/rr/scitech/mysteries/thunder.html
https://en.wikipedia.org/wiki/Thunder