圣艾爾摩之火

陳延洲

For those not familiar， “St. Elmos Fire” is a name for the glow1 that looks like blue violet fire surrounding the top of pointed metal objects during a storm.

為那些不熟悉它的人說明一下，“圣艾爾摩之火”是指在暴風(fēng)雨中金屬物尖端周圍所產(chǎn)生的如火焰般的藍(lán)紫色光。

This phenomenon2 can trace its name back to an Italian saint3 “St. Elmo” or “St. Erasmus” around 300 A.D.， the patron4 saint of early Mediterranean sailors. This glow tended to appear on the tops of the masts5 of ships during a thunderstorm. People believed that if St. Elmo appeared， it was a good omen6 and an answer to the sailors prayers7， as the seas would begin to die down and the winds would calm. If he （the glow） appeared during times of good weather， it was said that St. Elmos guiding hand was warning of a storm.

這種現(xiàn)象的名稱可以追溯到公元3世紀(jì)左右的意大利圣人“圣艾爾摩”，又名“圣伊拉斯謨”，他是早期地中海水手的守護(hù)神。在雷雨期間，這種光往往出現(xiàn)在船桅頂端。人們認(rèn)為，如果圣艾爾摩出現(xiàn)，那就是個好兆頭，是對水手祈禱的回應(yīng)，因為大海將平靜下來，風(fēng)將逐漸平息。如果這種光在天氣好的時候出現(xiàn)，據(jù)說那是圣艾爾摩的指引之手正發(fā)出警告，一場暴風(fēng)雨即將到來。

Charles Darwin even wrote about the phenomenon in a letter. He wrote about a night spent on a ship during a thunderstorm， “Everything was in flames， the sky with lightning， the water with luminous8 particles9， and even the very masts were pointed with a blue flame.”

查爾斯·達(dá)爾文甚至在一封信中寫到了這種現(xiàn)象。他寫到了雷雨中在一艘船上度過的一晚，“每樣?xùn)|西都像是著了火，天空在閃電，水里閃爍著發(fā)光的微粒，甚至連桅桿頂端都有藍(lán)色的火焰?！?/p>

Scientifically， this phenomenon is known as a “point discharge”. It can， and commonly does， happen at the tip of any conductive10 surface during thunderstorms. It can be seen on the tops of church steeples， lightning rods， the tips of airplane wings， and even blades of grass and the horns on cattle！

從科學(xué)上講，這種現(xiàn)象被稱為“尖端放電”。在雷雨期間，這種現(xiàn)象通常發(fā)生在任何導(dǎo)電的物體表面。在教堂的尖頂、避雷針的頂端、飛機(jī)機(jī)翼的尖端，甚至草葉和牛的尖角上都可以看到它！

Benjamin Franklin was the first to more or less correctly describe the phenomenon in 1749. He thought the “fire” was a way lightning rods would “draw out” a thunderstorms electricity slowly before it built up enough charge11 to form a strike.

在1749年，本杰明·富蘭克林是第一個或多或少正確描述這個現(xiàn)象的人。他認(rèn)為“火焰”是避雷針在雷暴積累足夠電荷以形成雷電之前，緩慢釋放雷暴電的一種方式。

So why does this happen during thunderstorms， and why does it happen more easily with pointed metal objects？

那么為什么在雷暴期間會發(fā)生這種情況呢？它又為什么會更容易發(fā)生在尖銳的金屬物體上呢？

A pointed conductor12 will have more electrons13 than an object that doesnt have a pointed tip， and therefore more charge， at its tip.

尖銳的導(dǎo)體比沒有尖端的物體帶有更多的電子，因此在它的尖端會有更多的電荷。

During thunderstorms， free electrons， positively charged ion clusters14 （at the surface of the ships mast） and the surrounding air， all colliding15 with each other in a form of matter known as plasma16. Plasma will give out light and give life to St. Elmo and his “fire”！

在雷雨期間，自由電子、（船桅表面的）正電荷離子簇和周圍的空氣，都以一種稱為等離子體的物質(zhì)形式相互碰撞?！?br>