時差N小時:地球磁場的變化(上)

You’re a polar explorer and you’ve just reached thenorth pole. The huskies are yapping, the camerasare ready and you’re just about to unfurl the flagwhen, all of a sudden, the north pole becomes thesouth pole. Imagine your chagrin. Okay, so itdoesn’t really happen that fast, but it’s true that inthe past the earth’s magnetic poles have switchedplaces. In fact, it seems to happen roughly every250,000 years or so. How do we know this? Whenlava is in its molten state, the atoms in it can movearound fairly easily. At this time some atoms, likeiron, will align themselves with the earth’s magnetic field in a recognizable way. Then, asthe lava solidifies into rock, these little compasses get frozen in position. It’s like writing yourname in wet cement.

【詞匯注釋】

unfurl v. 展開

all of a sudden 突然

chagrin n. 懊惱

roughly adv. 大概

lava n. 熔巖

align v.排列

solidify v.凝固

【參考譯文】

你是名極地探險者，你剛剛到達北極。愛斯基摩犬在狂吠，相機已經(jīng)準備好了，你正要展開旗幟，突然，北極變成了南極。想象下你的懊惱。事實上，磁場變換并沒有那么快。但是在過去地球的磁場確實發(fā)生了變換，事實上，大概每25萬年左右，磁場就要發(fā)生改變。我們是如何知道的?當熔巖處于融化狀態(tài)時，其中的原子能輕易地移動。這時候，有些原子比如鐵原子，以一種可識別的方式按照地球磁場的方向排列，當熔巖凝固成巖石時，這些小的指南針會在原地冷凝。這就像將你的名字寫在濕的水泥上。