• Czech: hřmění , dunění
• Finnish: jyrinä, jylinä, pauhu
• German: Donnern
• Hungarian: robaj
• Japanese: 轟音
• Polish: grzmot
• Russian: рокот
• Scottish Gaelic: tàirneanach
• Slovene: grmenje
• Swedish: mullrande , dån

• Breton: ober kurun, taranal / taraniñ
• Czech: hřmít
• Dutch: donderen
• Finnish: ukkostaa, jyristä, pauhata
• French: tonner
• German: donnern
• Italian: tuonare
• Japanese: 轟音を立てる
• Polish: grzmieć, zagrzmieć
• Portuguese: trovoar, trovejar
• Russian: греметь (gr'em'ét’), грохотать (groχotát’)
• Slovene: grmeti
• Swedish: dundra, dåna
• Thai: (săaifáa fâat)

• Breton: taranal, taraniñ
• Czech: hřmít, hromovat
• Dutch: overdonderen
• Finnish: jyristä
• French: déblatérer
• Japanese: 怒鳴る
• Polish: gromić
• Portuguese: trovejar

• ttbc Esperanto: tondri
• ttbc French: foudroyer
• ttbc German: donnern
• Guaraní: sunu
• ttbc Indonesian: gelegar
• ttbc Interlingua: tonar
• ttbc Japanese: 雷が鳴る (かみなりがなる, kaminarí ga narú) This means 'it thunders.' I cannot sure this is a common English usage. by Eveningmist, 04:37, 9 January 2008 (UTC)
• ttbc Latin: tonare
• ttbc Norwegian: tordne
• Tupinambá: sunung
• ttbc Thai: (fáapàa)

Thunder is the sound made by lightning. Depending on the nature of the lightning and distance of the hearer, it can range from a sharp, loud crack to a long, low rumble. 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 sonic shock wave which produces the sound of thunder.

The cause of thunder

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 Aristotle in the third century BC, and an early speculation was that it was caused by the collision of 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 shock wave in the air due to the sudden thermal expansion of the plasma in the lightning channel. In a fraction of a second the air is heated to a temperature approaching 28,000 °C (50,000 °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, this consensus has been eroded by the observation that measured overpressures in simulated lightning are greater than what could be achieved by the amount of heating found. Alternative proposals rely on electrodynamic effects of the massive current acting on the plasma in the bolt of lightning.

Etymology

The d in thunder is epenthetic, and is now found in Modern Dutch donder, from earlier Old English þunor, Middle Dutch donre, together with Old Norse þorr, Old Frisian þuner, Old High German donar descended from Proto-Germanic *þunraz. In Latin it's tonare "to thunder" (see also tornado). The name of the Germanic god Thor comes from the Old Norse word for thunder.

The shared Proto-Indo-European root is *tón-r̥.

See also:

• Thursday (German: Donnerstag: "Thunders Day")
• Donner und Blitz (German for "Thunder and Lightning")
• Tornado

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 (like light) does not travel instantaneously, and that sound is by far the slower. 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 air is approximately 344 m/s or 1130 feet per second or 762 mph. The speed of light can be assumed to be infinite in this calculation because one must know that there has been a lightning strike before starting counting (based on the fact that human reaction takes aprox 0.5 seconds). Therefore, the lightning is approximately one kilometer distant for every 2.9 seconds (or one mile for every 4.6 seconds). In the same five seconds the light could have circled the globe 37 times. Thunder is seldom heard at distances over 24 kilometers (15 miles).

A flash of lightning and a simultaneous sharp "clap!" of thunder, a thunderclap, indicates that the lightning strike was very near.

Fear of thunder

Fear of thunder is known as astraphobia.

See also

• Thunderstorm
• Thunderbolt
• Lightning
• The Castle Thunder sound effect
• List of thunder gods
• Thunder gods category

References

External links

• The science of thunder

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