時(shí)差N小時(shí):地球磁場(chǎng)改變的原因(上)

On a previous show we discussed how, every200,000 years or so, the north and south polesswitch places. Not that the places themselves move—rather, the entire magnetic field of the earthflips around, resulting in the pole we now call“north” being on the southern tip of the planet, andvice versa. Why does this happen? Although itseems pretty solid, the outer core of our planet isin a molten state. That means it’s partway betweenwhat most folks would call liquid and solid. Much ofthis molten interior is iron and nickel. These areelements that conduct electricity very well. It’s the fluid metals that move about inside earththat generate a magnetic field around our entire planet. Although from close up these metalsare bubbling like hot soup, you could also say that in general their motions follow a prettysteady pattern. That’s why the magnetic field on earth is pretty stable.

【生詞注釋】

switch v.轉(zhuǎn)換

magnetic field 磁場(chǎng)

flip vt.快速翻動(dòng)

tip n. 頂端

solid adj. 固體的, 堅(jiān)固的

molten adj. 熔化的

partway adv. 到某種程度

interior n. 內(nèi)部

close up n. 靠近

bubble v. 冒泡, 沸騰

【參考譯文】

在先前的節(jié)目中我們討論了每隔20萬(wàn)年，地球的南北極都要互換位置，不僅是地點(diǎn)的移動(dòng)，而是整個(gè)地球的磁場(chǎng)快速翻轉(zhuǎn)，導(dǎo)致我們現(xiàn)在稱作“北極”的地方原來(lái)在地球的南端，正好與原來(lái)磁場(chǎng)相反。這種現(xiàn)象為什么會(huì)發(fā)生呢?盡管地球的外殼看起來(lái)很牢固，實(shí)際上它處于融化的狀態(tài)中，那意味著地殼處于液體和固體間的中間形態(tài)。這種溶化物質(zhì)的大部分組成部分是鐵和鎳。這些都是極易導(dǎo)電的物質(zhì)。它們也是在地球內(nèi)部流動(dòng)的液體金屬，從而形成了整個(gè)地球的磁場(chǎng)。盡管從近處看，這些金屬就像熱湯那樣冒泡，你也可以說(shuō)從整體上來(lái)看，他們的運(yùn)動(dòng)遵循著一種十分穩(wěn)定的模式。那也是地球磁場(chǎng)十分穩(wěn)定的原因。