Editing Thunder

{{Short description|Sound produced by lightning}}
{{hatnote group|
{{Other uses}}
{{Distinguish|lightning}}
}}{{Listen
| filename     = Thunder.ogg
| title        = Rain
| description  = Typical sound of [[rain]] with [[thunder]]
| format       = [[Ogg]]
}}
'''Thunder''' is the [[sound]] caused by [[lightning]].<ref name="NSSL">{{cite web|url=https://www.nssl.noaa.gov/education/svrwx101/lightning/faq/ |title=Severe Weather 101: Lightning Basics|website=nssl.noaa.gov|access-date=October 23, 2019}}</ref><ref name="FJFK: Thunder Facts">{{cite web|url=https://www.factsjustforkids.com/weather-facts/thunder-facts-for-kids.html |title=Thunder Facts|website=factsjustforkids.com|access-date=October 23, 2019}}</ref><ref name="NWS">{{cite web|url=https://www.weather.gov/jetstream/thunder |title=The Sound of Thunder|website=weather.gov|access-date=October 23, 2019}}</ref> Depending upon the distance from and nature of the lightning, it can range from a long, low rumble to a sudden, loud crack. The sudden increase in [[temperature]] and hence [[pressure]] caused by the lightning produces rapid [[Thermal expansion|expansion of the air]] in the path of a [[Lightning strike|lightning bolt]].<ref>{{cite web |url=https://scijinks.gov/lightning/ |title=What Causes Lightning and Thunder? |publisher=NOAA |date=2022}}</ref> In turn, this expansion of air creates a [[Shock wave|sonic shock wave]], often referred to as a "thunderclap" or "peal of thunder". The scientific study of thunder is known as ''brontology'' and the irrational fear ([[phobia]]) of thunder is called ''brontophobia''.

== Etymology==
The ''d'' in [[Modern English]] ''thunder'' (from earlier [[Old English]] ''þunor'') is [[epenthetic]], and is now found as well in Modern Dutch ''donder'' (cf. [[Middle Dutch]] ''donre''; also [[Old Norse]] ''[[þorr]]'', [[Old Frisian]] ''þuner'', [[Old High German]] ''donar'', all ultimately descended from [[Proto-Germanic]] *''þunraz''). In [[Latin]] the term was ''tonare'' "to thunder". The name of the [[Nordic_countries|Nordic]] god [[Thor]] comes from the [[Old Norse language|Old Norse]] word for thunder.<ref>{{cite book|title=Oxford English Dictionary|edition=2|year=1989|publisher=Oxford University Press|location=Oxford, England|chapter=thunder|title-link=Oxford English Dictionary}}</ref>

The shared [[Proto-Indo-European language|Proto-Indo-European root]] is [[wikt:Appendix:List of Proto-Indo-European roots#t|*''tón-r̥'']] or ''*{{PIE|tar-}}'', also found in Gaulish ''[[Taranis]]''.<ref>Matasovic, Ranko. ''Etymological Dictionary of Proto Celtic''. Leiden, The Netherlands: Brill. 2009. p. 384. {{ISBN|978-90-04-17336-1}}</ref>

==Cause==
The cause of thunder has been the subject of centuries of speculation and scientific [[inquiry]].<ref name = Vavreketaln.d.>{{Cite web |last1=Vavrek |first1=R. J. |last2=Kithil |first2=R. |last3=Holle |first3=R. L. |last4=Allsopp |first4=J. |last5=Cooper |first5=M. A. |date=17 July 2006 |orig-year=4 April 2006 |title=Section 6.1.8: The Science of Thunder |url=http://lightningsafety.com/nlsi_info/thunder2.html |archive-url=https://web.archive.org/web/20060717060557/http://lightningsafety.com/nlsi_info/thunder2.html |archive-date=17 July 2006 |publisher=National Lightning Safety Institute |access-date=11 June 2022}}</ref> Early thinking was that it was made by deities, but the ancient [[Ancient Greek philosophy|Greek philosophers]] attributed it to natural causes, such as wind striking [[cloud|clouds]] ([[Anaximander]], [[Aristotle]]) and [[Airflow|movement of air]] within clouds ([[Democritus]]).<ref name="Heidorn1999">{{cite web|last=Heidorn|first= Keith C. |year=1999|title= Thunder: Voice of the heavens|url=http://www.islandnet.com/~see/weather/elements/thunder1.htm|archive-url=https://web.archive.org/web/19991023022742/http://www.islandnet.com/~see/weather/elements/thunder1.htm |archive-date=1999-10-23}}</ref> The Roman philosopher [[Lucretius]] held it was from the sound of [[hail]] colliding within clouds.<ref name = Heidorn1999 /> By the mid-19th century, the accepted theory was that lightning produced a [[vacuum]] and that the collapse of that vacuum produced what is known as thunder.<ref name = Vavreketaln.d. />

Scientists have agreed since the 20th century that thunder must begin with a [[shock wave]] in the air due to the sudden thermal expansion of the [[plasma (physics)|plasma]] in the lightning channel.<ref name="UmanVladimir A. Rakov2007">{{cite book|last1=Rakov|first1=Vladimir A. |last2=Uman|first2=Martin A.|title=Lightning: Physics and Effects|year=2007|publisher=[[Cambridge University Press]]|location=Cambridge, England|isbn=978-0-521-03541-5|page=378}},</ref><ref name = Heidorn1999 /> The temperature inside the lightning channel, measured by [[Spectroscopy|spectral analysis]], varies during its 50 [[Microsecond|μs]] existence, rising sharply from an initial temperature of about 20,000&nbsp;[[Kelvin|K]] to about 30,000&nbsp;K, then dropping away gradually to about 10,000&nbsp;K. The average is about {{convert|20400|K|C F}}.<ref>{{cite book|last=Cooray|first=Vernon|title=The lightning flash|url=https://archive.org/details/lightningflashpo00coor|url-access=limited|publisher=[[Institution of Electrical Engineers]]|location=London|year=2003|pages=[https://archive.org/details/lightningflashpo00coor/page/n187 163]–164|isbn=978-0-85296-780-5}}</ref> This heating causes a rapid outward expansion, impacting the surrounding cooler air at a speed faster than sound would otherwise travel. The resultant outward-moving pulse is a shock wave,<ref name="britannica">{{cite encyclopedia | url =http://www.britannica.com/EBchecked/topic/594339/thunder | title =Thunder | encyclopedia =Encyclopædia Britannica | access-date =2008-09-12 | url-status =live | archive-url =https://web.archive.org/web/20080607020659/http://www.britannica.com/EBchecked/topic/594339/thunder | archive-date =2008-06-07 }}</ref> similar in principle to the shock wave formed by an [[explosion]], or at the front of a [[supersonic]] [[aircraft]]. Near the source, the [[Sound pressure|sound pressure level]] of thunder is usually 165 to 180 [[Decibel|dB]], but can exceed 200&nbsp;dB in some cases.<ref>{{Cite web|title=Ultimate Sound Pressure Level Decibel Table|url=http://makeitlouder.com/Decibel%20Level%20Chart.txt|access-date=2020-12-13}}</ref>

Experimental studies of simulated lightning have produced results largely consistent with this model, though there is continued debate about the precise physical mechanisms of the process.<ref>{{cite book | last1 = MacGorman | first1 = Donald R. | last2 = Rust | first2 = W. David | title = The Electrical Nature of Storms | publisher = [[Oxford University Press]] | year = 1998 | pages = 102–104 | url = https://books.google.com/books?id=_NbHNj7KJecC | access-date = 2012-09-06 | isbn = 978-0195073379 | url-status = live | archive-url = https://web.archive.org/web/20140628073642/http://books.google.com/books?id=_NbHNj7KJecC | archive-date = 2014-06-28 }}</ref><ref name="UmanVladimir A. Rakov2007"/> Other causes have also been proposed, relying on [[electrodynamic]] effects of the enormous current acting on the plasma in the bolt of lightning.<ref>{{cite journal|author=P Graneau|title= The cause of thunder|year= 1989 |journal=J. Phys. D: Appl. Phys. |volume=22 |pages=1083–1094 |doi=10.1088/0022-3727/22/8/012|issue=8|bibcode = 1989JPhD...22.1083G |s2cid= 250836715}}</ref>

==Consequences==
The shock wave in thunder is sufficient to cause property damage<ref name = Vavreketaln.d. /> and injury, such as internal [[contusion]], to individuals nearby.<ref>{{cite book|last=Fish|first=Raymond M|editor=Nabours, Robert E|title=Electrical injuries: engineering, medical, and legal aspects|year=2021|publisher=Lawyers & Judges Publishing|location=Tucson, AZ|isbn=978-1-930056-71-8|page=[https://archive.org/details/electricalinjuri02ednabo/page/220 220]|chapter=Thermal and mechanical shock wave injury|chapter-url=https://archive.org/details/electricalinjuri02ednabo/page/220}}</ref> Thunder can rupture the [[eardrum]]s of people nearby, leading to permanently [[hearing loss|impaired hearing]].<ref name = Vavreketaln.d. /> Even if not, it can lead to temporary deafness.<ref name = Vavreketaln.d. />

==Types==
Vavrek et al. (n.d.) reported that the sounds of thunder fall into categories based on [[loudness]], duration, and [[Pitch (music)|pitch]].<ref name = Vavreketaln.d. /> ''Claps'' are loud sounds lasting 0.2 to 2 seconds and containing higher pitches. ''Peals'' are sounds changing in loudness and pitch. ''Rolls'' are irregular mixtures of loudness and pitches. ''Rumbles'' are less loud, last for longer (up to more than 30 seconds), and are of low pitch.<ref>{{cite web |url=https://www.fastfactsforkids.com/weather-facts/thunder-facts-for-kids |title=Thunder Facts |publisher=Fast Facts for Kids |date=2022}}</ref>

Inversion thunder results when lightning strikes occur between the cloud and ground during a [[Inversion (meteorology)|temperature inversion]]. The resulting thunder sounds have significantly greater acoustic energy than those produced from the same distance in non-inversion conditions. In a temperature inversion, the air near the ground is cooler than the air higher up. Inversions often happen when warm, moist air passes above a cold front. Within a temperature inversion, sound energy is prevented from dispersing vertically as it would in non-inversion conditions, and is thus concentrated in the near-ground layer.<ref>{{cite web|author=Dean A. Pollet and Micheal M. Kordich|url=https://apps.dtic.mil/sti/pdfs/ADA477220.pdf|title=User's guide for the Sound Intensity Prediction System (SIPS) as installed at the Naval Explosive Ordnance Disposal Technology Division (Naveodtechdiv)|archive-url=https://web.archive.org/web/20130408130804/http://www.dtic.mil/CGI-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA477220|date=2013-04-08|archive-date=April 8, 2013|url-status=live|publisher=Systems Department February 2000. dtic.mil}}</ref>

Cloud-to-ground lightning (CG) typically consists of two or more return strokes, from ground to cloud. Later return strokes have greater acoustic energy than the first.<ref>{{cite web |url=https://www.nssl.noaa.gov/education/svrwx101/lightning/types/ |title=Lightning Types |publisher=NOAA National Severe Storms Laboratory |date=2022}}</ref>

== Perception ==
{{Listen
| filename     = Very close thunder cracks.flac
| title        = Thundercracks
| description  = Sample of sharp cracking sounds of thunder heard immediately after nearby lightning strikes
| format       = [[Flac]]
| filename2    = Thunder crack 2B.ogg
| title2       = Crack of thunder
| description2 = A ''crack of thunder'' during the sound of falling rain
| filename3    = Booming Thunder 2023-10-09 2-07-34 am.ogg
| title3       = Thunder boom
| description3 = A ''thunder boom''
}}

The most noticeable aspect of lightning and thunder is that the lightning is seen before the thunder is heard. This is a consequence of the [[speed of light]] being much greater than the [[speed of sound]]. The speed of sound in dry air is approximately {{Convert|343|m/s|ft/s|abbr=on}} or {{convert|1236|km/h|mi/h|abbr=on}} at {{Convert|20|C|F K}}.<ref>{{cite book |title=Handbook of Chemistry and Physics, 72nd edition, special student edition |page=14.36|publisher=The Chemical Rubber Co. |year=1991 |location=Boca Raton |isbn=978-0-8493-0486-6}}</ref> 

This translates to approximately {{Convert|3|s/km|s/mi|abbr=on}}; saying "one thousand and one... one thousand and two..." is a useful method of counting the seconds from the perception of a given lightning flash to the perception of its thunder (which can be used to gauge the proximity of lightning for the sake of safety). To estimate the distance from the lightning strike, divide the counted seconds by five for miles,<ref>{{cite web |date=2022 |title=Understanding Lightning: Thunder |url=https://www.weather.gov/safety/lightning-science-thunder |publisher=National Weather Service}}</ref> or three for kilometers.  

A very bright flash of lightning and an almost simultaneous sharp "crack" of thunder, a ''thundercrack'', therefore indicates that the lightning strike was very near.

Close-in lightning has been described first as a clicking or cloth-tearing sound, then a cannon shot sound or loud crack/snap, followed by continuous rumbling.<ref name = Vavreketaln.d. /> The early sounds are from the leader parts of lightning, then the near parts of the return stroke, then the distant parts of the return stroke.<ref name = Vavreketaln.d. />

==See also==
* [[Brontophobia]] (fear of thunder)
* [[Castle thunder (sound effect)|Castle Thunder sound effect]]
* [[Lightning]]
* [[List of thunder gods]]
* [[Mistpouffers]]
* [[Sonic boom]]
* [[Thunderbolt]]
* [[Thunderstorm]]

== References ==
{{Reflist}}

==External links==
{{Commons category|Thunder}}
{{Wikiquote}}
{{Wikibooks|Engineering Acoustics/Thunder acoustics}}
* [http://www.lightningsafety.com/nlsi_info/thunder2.html The Science of Thunder] {{Webarchive|url=https://web.archive.org/web/20071015104133/http://lightningsafety.com/nlsi_info/thunder2.html |date=2007-10-15 }}—National Lightning Safety Institute
* [https://web.archive.org/web/19990909060128/http://www.islandnet.com/~see/weather/elements/thunder2.htm Thunder: A Child of Lightning] by Keith C. Heidorn, PhD, ACM
* [https://www.pluviophile.com Storm: Thunder sounds in binaural audio]

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[[Category:Lightning]]
[[Category:Noise]]
[[Category:Severe weather and convection]]
[[Category:Meteorological phenomena]]

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