# Acoustics/Generation and Propagation of Thunder

**Thunder** is the sound made by lightning. Depending on the nature of
the lightning and distance of the listener, 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 which produces the sound of
thunder, often referred to as a *clap*, *crack*, or *peal of thunder*.
The distance of the lightning can be calculated by the listener
depending on when the sound is heard vs. the vision of the lightning
strike.

!A lightning bolt.{width="350"}

## Etymology

The *d* in Modern English *thunder* (from earlier Old English *þunor*)
is epenthetic, and is now found as well in Modern Dutch *donder* (cp
Middle Dutch *donre*, and Old Norse *þorr*, Old Frisian *þuner*, Old
High German *donar* descended from Proto-Germanic \**þunraz*). In Latin
the term was *tonare* \"to thunder\". The name of the Germanic god Thor
comes from the Old Norse word for thunder.

***NOTE*:The text above is taken from the wikipedia
entry.**

