Thunder

雷是由閃電引起的衝擊波。因為聲音和光在大氣中的傳播速度不同，人們可以通過計算它們之間的時間間隔來確定閃電發生的距離。在空氣之中，聲速大約為340米 (單位)米/秒，因此閃電發生的地點大約為每間隔3秒一公里（或5秒一英里）。

雷擊其實就是閃電電了一下，不過電量比較大，有的建築物會倒塌，樹會斷，人畜可能死傷。中國古代認為雷擊跟天譴有關，比如做了不孝之事，天公震怒，將犯罪嫌疑人電死以示懲戒。要預防雷擊之災，避雷針將雷電導向地線。

Thunder =雷

圖片參考：http://upload.wikimedia.org/wikipedia/commons/thumb/3/36/Thunder.jpg/350px-Thunder.jpg



圖片參考：http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png
A thunderstorm over Piracicaba, Brazil

Thunder is, even today, not completely understood by science. The word usually describes a sonic shock wave caused by the rapid heating and expansion of the air surrounding and within a bolt of lightning. The bolt changes the air into plasma and it instantly explodes, causing the sound known as a thunder clap.
This phenomenon occurs at the same time as a lightning flash, but a thunder clap is usually heard after lightning is seen because light travels faster (186,000 miles / 299,338 kilometers per second) than sound (around 700 miles / 1,126 kilometers per hour, varying depending on temperature, humidity and air pressure).
Fear of thunder is called astraphobia.
Theories of 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 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 along its path, and that thunder was caused by the subsequent motion of air rushing to fill the vacuum. Later in the 19th century it was believed that thunder was caused by an explosion of steam when water along the lightning channel was heated. Another theory was that gaseous materials were created by lightning and then exploded. 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.

Dangerous noise levels
Added to the dangers already present in lightning, thunder is extremely loud, registering at approximately 120 decibels, about the same as most firearms. This high sound level can cause immediate damage to the inner ear.[1] Three minutes of exposure to thunder will cause permanent Noise-induced hearing loss.[2]


圖片參考：http://upload.wikimedia.org/wikipedia/commons/thumb/d/da/Rolling-thunder-cloud.jpg/350px-Rolling-thunder-cloud.jpg



圖片參考：http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png
A rolling thunderstorm (Cumulonimbus arcus) photographed on July 17, 2004 in Enschede, The Netherlands by John Kerstholt.

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, built on a PIE stem *(s)tene- also found in Sanskrit tana-itnu- "thundering", Latin tonare "to thunder" (see also tornado). The name of the Germanic god Thor comes from the Old Norse word for thunder.

Calculating distance
Since sound and light travel at different speeds through the atmosphere, one can estimate how far away the bolt of lightning is by timing the interval between seeing the flash and hearing the thunder. The speed of sound in air is approximately 340 m/s (761 mph). The speed of light is so fast that it can be ignored in this calculation. Therefore, the lightning is approximately one kilometer distant for every three seconds (or one mile for every five seconds). Thunder is seldom heard at distances over 15 miles.
雷是由閃電引起的衝擊波。因為聲音和光在大氣中的傳播速度不同，人們可以通過計算它們之間的時間間隔來確定閃電發生的距離。在空氣之中，聲速大約為340米 (單位)米/秒，因此閃電發生的地點大約為每間隔3秒一公里（或5秒一英里）。
雷擊其實就是閃電電了一下，不過電量比較大，有的建築物會倒塌，樹會斷，人畜可能死傷。中國古代認為雷擊跟天譴有關，比如做了不孝之事，天公震怒，將犯罪嫌疑人電死以示懲戒。要預防雷擊之災，避雷針將雷電導向地線。

1. 雷,雷聲[U]
After the lightning came the thunder.
閃電後接著是雷聲。
2. 似雷的響聲,轟隆聲[C][U]
We could hear the thunder of distant cannons.
我們可以聽到遠處大砲的轟隆聲。
3. 惱怒;譴責;威嚇,恐嚇[C][U]
vi.
1. (以it為主詞)打雷
It thundered several times, but no rain fell.
打了幾次雷,卻沒下雨。
2. 發出雷鳴般響聲;轟隆隆地移動[Q]
Trucks thundered down the highway.
大卡車從公路上轟隆隆地開過去。
3. 怒喝,大聲斥責;威嚇[(+at/against)]
They thundered against cheating on exams.
他們大聲疾呼反對考試作弊。
vt.
1. 轟隆地發出;砰然重擊[(+out)]
2. 厲聲發出(威脅,警告等)吼出[(+at)]
The boss thundered out his orders at me.
老板對我吼叫著發號施令。

thunder
1. 雷,雷聲
2. 似雷的響聲,轟隆聲
3. 惱怒;譴責;威嚇,恐嚇