Every so often, however, that regular motion is interrupted. Think of what happens when you stir that bubbling soup. It takes a few minutes for things to settle down and the regular pattern of bubbling to resume. That’s probably what happens inside earth. Something–maybe nothing more than naturally occurring variations in the process– disrupts the otherwise regular flow of metals in our planet. This shuts off the magnetic field for a while. Eventually, things start bubbling away again and the magnetic field returns. When it comes back on, one end will be north and one end will be south. Whether or not they were aligned that way before the disturbance is a matter of chance.

【生詞注釋】
interrupt v.打斷
settle down 平靜下來
resume v. 重新開始
variation n.變化
align vi.排行
disturbance n.擾亂

【參考譯文】
盡管如此，常規的運動不時被打斷。想想當你捅破熱湯中的氣泡時，發生的狀況。得需要幾分鐘熱湯才能平靜襲來，正常的冒泡形式才會重新開始。那也可能是地球內部的模式。有些物質——很可能是是自然變化過程中的物質——打斷了地球內部金屬的正常流動。這導致磁場失效了一段時間。最終，冒泡過程重新開始，磁場重新出現。當磁場重現出現時，一端是北極，另一段是南極。在磁場被阻斷錢它們是否按照那種方式派別完全是隨機的。