他们声称地球的自转和地球的磁极的关系不稳定，预示着平均每40万年就有一次的磁极颠倒。
They claim a relationship between the rotation and the magnetic polarity of Earth, which does change irregularly, with a magnetic reversal taking place every 400,000 years on average.
这种磁极颠倒在418万年前曾发生过一次，CAC地区的沉积物中就留下了这次颠倒发生过的痕迹。
One of these polarity flip-flops, known to have occurred 4.18 million years ago, left its mark in sediments in the CAC.
到底什么时候磁极将会颠倒从目前已知的证据中去预测还不能做到，但对此最适宜的猜测便是那一天的到来是好几个世纪以后的事情了。
Just when the magnetic field will flip is impossible to predict from what is known at the moment; the best guess is that there are still several centuries to go.
为什么每几十万年，磁场磁极就会自我颠倒一下呢？
Why does the field spontaneously reverse itself every few hundred thousand years?
为什么每几十万年，磁场磁极就会自我颠倒一下呢？
Why does the field spontaneously reverse itself every few hundred thousand years?
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