system
Given the following post, respond as if you're commenting on Reddit:
human
Why does lightening, something that only lasts a fraction of a second, produce thunder that can last several seconds? 

What kind of acoustic trickery is going on here..? 
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Edit: a little more thought. I assume (maybe)in an urban environment the sound being able to reverberate and echo off of all of the buildings and structures could build up to a lengthy reverb, but why over a large empty field does it produce a rolling thunder lasting 15 or so seconds instead of just a "pop" or "crack"?
gpt
It's all kinds of echos and also, the lightning is what, like a mile long? It's not a point source. The sound that is produced near the ground gets to you much earlier than the sound produced at the top of the lightning. And everything in between gets to you in between, in a continuous way. Since the speed of sound is so slow, it's very noticeable.