Changes

==Origin==

==Origin==

[https://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English] thoner, thunder, from [https://nordan.daynal.org/wiki/index.php?title=English#ca._600-1100.09THE_OLD_ENGLISH.2C_OR_ANGLO-SAXON_PERIOD Old English] thunor; akin to Old High German thonar thunder, [[Latin]] tonare to thunder. The name of the Germanic god [http://en.wikipedia.org/wiki/Thor Thor] comes from the Old Norse [[word]] for thunder.

[https://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English] thoner, thunder, from [https://nordan.daynal.org/wiki/index.php?title=English#ca._600-1100.09THE_OLD_ENGLISH.2C_OR_ANGLO-SAXON_PERIOD Old English] thunor; akin to Old High German thonar thunder, [[Latin]] tonare to thunder. The name of the Germanic god [https://en.wikipedia.org/wiki/Thor Thor] comes from the Old Norse [[word]] for thunder.

*[http://en.wikipedia.org/wiki/12th_century before 12th Century]

*[https://en.wikipedia.org/wiki/12th_century before 12th Century]

==Definitions==

==Definitions==

*1: the [[sound]] that follows a flash of [[lightning]] and is caused by sudden expansion of the [[air]] in the path of the [[electrical]] discharge

*1: the [[sound]] that follows a flash of [[lightning]] and is caused by sudden expansion of the [[air]] in the path of the [[electrical]] discharge

*3: bang, rumble <the thunder of big guns>

*3: bang, rumble <the thunder of big guns>

==Description==

==Description==

'''Thunder''' is the [[sound]] made by '''[http://en.wikipedia.org/wiki/Lightning lightning]'''. Depending on the [[nature]] of the lightning and distance of the listener, thunder can range from a sharp, loud crack to a long, low rumble (brontide). The sudden increase in [[pressure]] and [[temperature]] from lightning produces rapid expansion of the [[air]] surrounding and within a bolt of lightning. In turn, this expansion of air creates a [http://en.wikipedia.org/wiki/Sonic_boom sonic shock wave] which produces the [[sound]] of thunder, often referred to as a clap, crack, or peal of thunder. The distance of the lightning can be [[calculated]] by the [[listener]] based on the time [[interval]] from when the lightning is seen to when the sound is heard.

'''Thunder''' is the [[sound]] made by '''[https://en.wikipedia.org/wiki/Lightning lightning]'''. Depending on the [[nature]] of the lightning and distance of the listener, thunder can range from a sharp, loud crack to a long, low rumble (brontide). The sudden increase in [[pressure]] and [[temperature]] from lightning produces rapid expansion of the [[air]] surrounding and within a bolt of lightning. In turn, this expansion of air creates a [https://en.wikipedia.org/wiki/Sonic_boom sonic shock wave] which produces the [[sound]] of thunder, often referred to as a clap, crack, or peal of thunder. The distance of the lightning can be [[calculated]] by the [[listener]] based on the time [[interval]] from when the lightning is seen to when the sound is heard.

==Cause==

==Cause==

The [[cause]] of thunder has been the subject of centuries of [[speculation]] and [[scientific]] [[inquiry]]. The first recorded [[theory]] is attributed to the [[Greek]] philosopher [http://en.wikipedia.org/wiki/Aristotle Aristotle] in the third century BC, and an early speculation was that it was caused by the collision of [http://en.wikipedia.org/wiki/Clouds clouds]. Subsequently, numerous other theories have been proposed. By the mid-19th century, the [[accepted]] [[theory]] was that lightning produced a [[vacuum]]. In the 20th century a [[consensus]] evolved that thunder must begin with a [http://en.wikipedia.org/wiki/Shock_wave shock wave] in the air due to the sudden thermal expansion of the [[plasma]] in the lightning channel. The [[temperature]] inside the lightning channel, measured by [http://en.wikipedia.org/wiki/Spectroscopy spectral analysis], varies during its 50 μs existence, rising sharply from an initial temperature of about 20,000 K to 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). This heating causes it to expand outward, plowing into the [[surrounding]] cooler air at a [[speed]] faster than [[sound]] would travel in that cooler air. The outward-moving [[pulse]] that results is a shock wave, similar in principle to the shock wave formed by an explosion, or at the front of a supersonic aircraft. More recently, the [[consensus]] around the cause of the shock wave has been eroded by the [[observation]] that measured overpressures in simulated lightning are greater than could be achieved by the amount of heating found. Alternative proposals rely on [http://en.wikipedia.org/wiki/Electrodynamic electrodynamic] [[effects]] of the massive current acting on the [[plasma]] in the bolt of lightning. This shockwave is sufficient to cause [[injury]], such as internal [http://en.wikipedia.org/wiki/Contusion contusion], to [[individuals]] nearby.  

The [[cause]] of thunder has been the subject of centuries of [[speculation]] and [[scientific]] [[inquiry]]. The first recorded [[theory]] is attributed to the [[Greek]] philosopher [https://en.wikipedia.org/wiki/Aristotle Aristotle] in the third century BC, and an early speculation was that it was caused by the collision of [https://en.wikipedia.org/wiki/Clouds clouds]. Subsequently, numerous other theories have been proposed. By the mid-19th century, the [[accepted]] [[theory]] was that lightning produced a [[vacuum]]. In the 20th century a [[consensus]] evolved that thunder must begin with a [https://en.wikipedia.org/wiki/Shock_wave shock wave] in the air due to the sudden thermal expansion of the [[plasma]] in the lightning channel. The [[temperature]] inside the lightning channel, measured by [https://en.wikipedia.org/wiki/Spectroscopy spectral analysis], varies during its 50 μs existence, rising sharply from an initial temperature of about 20,000 K to 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). This heating causes it to expand outward, plowing into the [[surrounding]] cooler air at a [[speed]] faster than [[sound]] would travel in that cooler air. The outward-moving [[pulse]] that results is a shock wave, similar in principle to the shock wave formed by an explosion, or at the front of a supersonic aircraft. More recently, the [[consensus]] around the cause of the shock wave has been eroded by the [[observation]] that measured overpressures in simulated lightning are greater than could be achieved by the amount of heating found. Alternative proposals rely on [https://en.wikipedia.org/wiki/Electrodynamic electrodynamic] [[effects]] of the massive current acting on the [[plasma]] in the bolt of lightning. This shockwave is sufficient to cause [[injury]], such as internal [https://en.wikipedia.org/wiki/Contusion contusion], to [[individuals]] nearby.  

==Calculating Distance==

==Calculating Distance==

A flash of lightning, followed after some seconds by a rumble of thunder is, for many people, the first [[illustration]] of the [[fact]] that [[sound]] [[travels]] significantly slower than [[light]]. Using this [[difference]], one can estimate how far away the bolt of lightning is by timing the [[interval]] between seeing the flash and hearing thunder. The speed of sound in dry air is approximately 343 m/s or 1,127 feet per second or 768 mph (1,236 km/h) at 20°C (68 °F). However, this figure can only be used as an approximation of the speed of a thunder-clap, as you are unlikely to find dry air in a thunderstorm.

A flash of lightning, followed after some seconds by a rumble of thunder is, for many people, the first [[illustration]] of the [[fact]] that [[sound]] [[travels]] significantly slower than [[light]]. Using this [[difference]], one can estimate how far away the bolt of lightning is by timing the [[interval]] between seeing the flash and hearing thunder. The speed of sound in dry air is approximately 343 m/s or 1,127 feet per second or 768 mph (1,236 km/h) at 20°C (68 °F). However, this figure can only be used as an approximation of the speed of a thunder-clap, as you are unlikely to find dry air in a thunderstorm.