Editing Lightning (section)

=== Noise (Thunder) ===
{{main|Thunder}}

Because the electrostatic discharge of terrestrial lightning superheats the air to plasma temperatures along the length of the discharge channel in a short duration, [[kinetic theory of gases|kinetic theory]] dictates gaseous molecules undergo a rapid increase in pressure and thus expand outward from the lightning creating a [[shock wave]] audible as thunder. Since the sound waves propagate not from a single point source but along the length of the lightning's path, the sound origin's varying distances from the observer can generate a rolling or rumbling effect. Perception of the sonic characteristics is further complicated by factors such as the irregular and possibly branching geometry of the lightning channel, by [[echo (phenomenon)|acoustic echoing]] from terrain, and by the usually multiple-stroke characteristic of the lightning strike.<ref>{{cite web |url=https://www.nationalgeographic.com/environment/article/lightning |work=[[National Geographic]] |title=Lightning|date=October 9, 2009 }}</ref> Thunder is heard as a rolling, gradually dissipating rumble because the sound from different portions of a long stroke arrives at slightly different times.<ref name=autogenerated1>[[#Uman|Uman (1986)]] pp. 103–110</ref>

Lightning at a sufficient distance may be seen and not heard; there is data that a lightning storm can be seen at over {{convert|100|mi|km|order=flip|abbr=in}} whereas the thunder travels about {{convert|20|mi|km|order=flip|abbr=in}}. Anecdotally, there are many examples of people describing a 'storm directly overhead' or 'all-around' and yet 'no thunder'. Since thunderclouds can be up to {{convert|20|km|mi|abbr=in}} high,<ref>{{Cite web|url=https://factfile.org/10-facts-about-cumulonimbus-clouds|title = 10 Facts about Cumulonimbus Clouds|date = May 17, 2016}}</ref> lightning occurring high up in the cloud may appear close but is actually too far away to produce noticeable thunder.

==== The distance approximation trick ====
[[Speed of light|Light travels]] at about {{cvt|300,000,000|m/s}}, while [[speed of sound|sound]] only travels through air at about {{cvt|343|m/s}}. An observer can approximate the distance to the strike by timing the interval between the visible lightning and the audible thunder it generates. A lightning flash preceding its thunder by one second would be approximately {{convert|343|m|mi|abbr=in}} away; thus a delay of three seconds would indicate a distance of about {{convert|1|km|mi|abbr=in}}; while a flash preceding thunder by five seconds would indicate a distance of roughly {{convert|1|mi|km|abbr=out}}. Consequently, a lightning strike observed at a very close distance will be accompanied by a sudden clap of thunder, with almost no perceptible time lapse, possibly accompanied by the smell of [[ozone]] (O<sub>3</sub>).