Thunder

Typical sound ofrainwiththunder

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Thunderis thesoundcaused bylightning.^[1]^[2]^[3]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 intemperatureand hencepressurecaused by the lightning produces rapidexpansion of the airin the path of alightning bolt.^[4]In turn, this expansion of air creates asonic shock wave,often referred to as a "thunderclap" or "peal of thunder". The scientific study of thunder is known asbrontologyand the irrational fear (phobia) of thunder is calledbrontophobia.

Etymology

ThedinModern Englishthunder(from earlierOld Englishþunor) isepenthetic,and is now found as well in Modern Dutchdonder(cf.Middle Dutchdonre;alsoOld Norseþorr,Old Frisianþuner,Old High Germandonar,all ultimately descended fromProto-Germanic*þunraz). InLatinthe term wastonare"to thunder". The name of theNordicgodThorcomes from theOld Norseword for thunder.^[5]

The sharedProto-Indo-European rootis*tón-r̥or*tar-,also found in GaulishTaranis.^[6]

Cause

The cause of thunder has been the subject of centuries of speculation and scientificinquiry.^[7]Early thinking was that it was made by deities, but the ancientGreek philosophersattributed it to natural causes, such as wind strikingclouds(Anaximander,Aristotle) andmovement of airwithin clouds (Democritus).^[8]The Roman philosopherLucretiusheld it was from the sound ofhailcolliding within clouds.^[8]By the mid-19th century, the accepted theory was that lightning produced avacuumand that the collapse of that vacuum produced what is known as thunder.^[7]

Scientists have agreed since the 20th century that thunder must begin with ashock wavein the air due to the sudden thermal expansion of theplasmain the lightning channel.^[9]^[8]The temperature inside the lightning channel, measured byspectral analysis,varies during its 50μsexistence, rising sharply from an initial temperature of about 20,000Kto about 30,000 K, then dropping away gradually to about 10,000 K. The average is about 20,400 K (20,100 °C; 36,300 °F).^[10]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,^[11]similar in principle to the shock wave formed by anexplosion,or at the front of asupersonic aircraft.Near the source, thesound pressure levelof thunder is usually 165 to 180dB,but can exceed 200 dB in some cases.^[12]

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.^[13]^[9]Other causes have also been proposed, relying onelectrodynamiceffects of the enormous current acting on the plasma in the bolt of lightning.^[14]

Consequences

The shock wave in thunder is sufficient to cause property damage^[7]and injury, such as internalcontusion,to individuals nearby.^[15]Thunder can rupture theeardrumsof people nearby, leading to permanentlyimpaired hearing.^[7]Even if not, it can lead to temporary deafness.^[7]

Types

Vavrek et al. (n.d.) reported that the sounds of thunder fall into categories based onloudness,duration, andpitch.^[7]Clapsare loud sounds lasting 0.2 to 2 seconds and containing higher pitches.Pealsare sounds changing in loudness and pitch.Rollsare irregular mixtures of loudness and pitches.Rumblesare less loud, last for longer (up to more than 30 seconds), and are of low pitch.^[16]

Inversion thunder results when lightning strikes occur between the cloud and ground during atemperature 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.^[17]

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.^[18]

Perception

Thundercracks

Sample of sharp cracking sounds of thunder heard immediately after nearby lightning strikes

Crack of thunder

Acrack of thunderduring the sound of falling rain

Thunder boom

Athunder boom

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The most noticeable aspect of lightning and thunder is that the lightning is seen before the thunder is heard. This is a consequence of thespeed of lightbeing much greater than thespeed of sound.The speed of sound in dry air is approximately 343 m/s (1,130 ft/s) or 1,236 km/h (768 mph) at 20 °C (68 °F; 293 K).^[19]

This translates to approximately 3 s/km (4.8 s/mi); 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,^[20]or three for kilometers.

A very bright flash of lightning and an almost simultaneous sharp "crack" of thunder, athundercrack,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.^[7]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.^[7]

References

^"Severe Weather 101: Lightning Basics".nssl.noaa.gov.RetrievedOctober 23,2019.
^"Thunder Facts".factsjustforkids.RetrievedOctober 23,2019.
^"The Sound of Thunder".weather.gov.RetrievedOctober 23,2019.
^"What Causes Lightning and Thunder?".NOAA. 2022.
^"thunder".Oxford English Dictionary(2 ed.). Oxford, England: Oxford University Press. 1989.
^Matasovic, Ranko.Etymological Dictionary of Proto Celtic.Leiden, The Netherlands: Brill. 2009. p. 384.ISBN 978-90-04-17336-1
^^a ^b ^c ^d ^e ^f ^g ^hVavrek, R. J.; Kithil, R.; Holle, R. L.; Allsopp, J.; Cooper, M. A. (17 July 2006) [4 April 2006]."Section 6.1.8: The Science of Thunder".National Lightning Safety Institute. Archived fromthe originalon 17 July 2006.Retrieved11 June2022.
^^a ^b ^cHeidorn, K. C. (1999). Thunder: Voice of the heavens. Retrieved fromhttp:// islandnet /~see/weather/elements/thunder1.htm
^^a ^bRakov, Vladimir A.; Uman, Martin A. (2007).Lightning: Physics and Effects.Cambridge, England:Cambridge University Press.p. 378.ISBN 978-0-521-03541-5.,
^Cooray, Vernon (2003).The lightning flash.London:Institution of Electrical Engineers.pp.163–164.ISBN 978-0-85296-780-5.
^"Thunder".Encyclopædia Britannica.Archivedfrom the original on 2008-06-07.Retrieved2008-09-12.
^"Ultimate Sound Pressure Level Decibel Table".Retrieved2020-12-13.
^MacGorman, Donald R.; Rust, W. David (1998).The Electrical Nature of Storms.Oxford University Press.pp. 102–104.ISBN 978-0195073379.Archivedfrom the original on 2014-06-28.Retrieved2012-09-06.
^P Graneau (1989). "The cause of thunder".J. Phys. D: Appl. Phys.22(8): 1083–1094.Bibcode:1989JPhD...22.1083G.doi:10.1088/0022-3727/22/8/012.S2CID 250836715.
^Fish, Raymond M (2021)."Thermal and mechanical shock wave injury".In Nabours, Robert E (ed.).Electrical injuries: engineering, medical, and legal aspects.Tucson, AZ: Lawyers & Judges Publishing. p.220.ISBN 978-1-930056-71-8.
^"Thunder Facts".Fast Facts for Kids. 2022.
^Dean A. Pollet and Micheal M. Kordich (2013-04-08)."User's guide for the Sound Intensity Prediction System (SIPS) as installed at the Naval Explosive Ordnance Disposal Technology Division (Naveodtechdiv)"(PDF).Systems Department February 2000. dtic.mil.Archivedfrom the original on April 8, 2013.
^"Lightning Types".NOAA National Severe Storms Laboratory. 2022.
^Handbook of Chemistry and Physics, 72nd edition, special student edition.Boca Raton: The Chemical Rubber Co. 1991. p. 14.36.ISBN 978-0-8493-0486-6.
^"Understanding Lightning: Thunder".National Weather Service. 2022.

External links

The Science of Thunder Archived2007-10-15 at theWayback Machine—National Lightning Safety Institute
Thunder: A Child of Lightningby Keith C. Heidorn, PhD, ACM
Storm: Thunder sounds in binaural audio

[NSSL-1] "Severe Weather 101: Lightning Basics".nssl.noaa.gov.RetrievedOctober 23,2019.

[FJFK:_Thunder_Facts-2] "Thunder Facts".factsjustforkids.RetrievedOctober 23,2019.

[NWS-3] "The Sound of Thunder".weather.gov.RetrievedOctober 23,2019.

[4] "What Causes Lightning and Thunder?".NOAA. 2022.

[5] "thunder".Oxford English Dictionary(2 ed.). Oxford, England: Oxford University Press. 1989.

[6] Matasovic, Ranko.Etymological Dictionary of Proto Celtic.Leiden, The Netherlands: Brill. 2009. p. 384.ISBN 978-90-04-17336-1

[Vavreketaln.d.-7] ^^a ^b ^c ^d ^e ^f ^g ^hVavrek, R. J.; Kithil, R.; Holle, R. L.; Allsopp, J.; Cooper, M. A. (17 July 2006) [4 April 2006]."Section 6.1.8: The Science of Thunder".National Lightning Safety Institute. Archived fromthe originalon 17 July 2006.Retrieved11 June2022.

[Heidorn1999-8] Heidorn, K. C. (1999). Thunder: Voice of the heavens. Retrieved fromhttp:// islandnet /~see/weather/elements/thunder1.htm

[UmanVladimir_A._Rakov2007-9] Rakov, Vladimir A.; Uman, Martin A. (2007).Lightning: Physics and Effects.Cambridge, England:Cambridge University Press.p. 378.ISBN 978-0-521-03541-5.,

[10] Cooray, Vernon (2003).The lightning flash.London:Institution of Electrical Engineers.pp.163–164.ISBN 978-0-85296-780-5.

[britannica-11] "Thunder".Encyclopædia Britannica.Archivedfrom the original on 2008-06-07.Retrieved2008-09-12.

[12] "Ultimate Sound Pressure Level Decibel Table".Retrieved2020-12-13.

[13] MacGorman, Donald R.; Rust, W. David (1998).The Electrical Nature of Storms.Oxford University Press.pp. 102–104.ISBN 978-0195073379.Archivedfrom the original on 2014-06-28.Retrieved2012-09-06.

[14] P Graneau (1989). "The cause of thunder".J. Phys. D: Appl. Phys.22(8): 1083–1094.Bibcode:1989JPhD...22.1083G.doi:10.1088/0022-3727/22/8/012.S2CID 250836715.

[15] Fish, Raymond M (2021)."Thermal and mechanical shock wave injury".In Nabours, Robert E (ed.).Electrical injuries: engineering, medical, and legal aspects.Tucson, AZ: Lawyers & Judges Publishing. p.220.ISBN 978-1-930056-71-8.

[16] "Thunder Facts".Fast Facts for Kids. 2022.

[17] Dean A. Pollet and Micheal M. Kordich (2013-04-08)."User's guide for the Sound Intensity Prediction System (SIPS) as installed at the Naval Explosive Ordnance Disposal Technology Division (Naveodtechdiv)"(PDF).Systems Department February 2000. dtic.mil.Archivedfrom the original on April 8, 2013.

[18] "Lightning Types".NOAA National Severe Storms Laboratory. 2022.

[19] Handbook of Chemistry and Physics, 72nd edition, special student edition.Boca Raton: The Chemical Rubber Co. 1991. p. 14.36.ISBN 978-0-8493-0486-6.

[20] "Understanding Lightning: Thunder".National Weather Service. 2022.

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