system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What makes thunder's sound?

How is it produced, and in general, what is it?
gpt
The thunder is a by-product of the lightning. When the lightning bolt travels through air, it very rapidly heats it. The air expands very rapidly as a result, causing a pressure wave to be created and travel through the air. Pressure waves in air = sound.