And the thing to know about REM sleep is it happens cyclically.

要知道，快速眼动睡眠是周性发生。

The Swiss historian Jean-Charles Sismondi was the first to identify the occurrence of periodic economic crises, but it was the work of a later economist, the Frenchman Charles Donoyer, 1786 to 1862, who revealed their cyclical form.

瑞士历史家让-夏尔·西是一个识别周性经济危机发生，但揭示其周性形式是后来经济家、法国人夏尔·多尼耶（1786年至1862年）工作。

Some studies suggest that it may be a recurring magnetic event that has affected  Earth for approximately 11 million years.

一些研究暗示，这可能是一个周性发生磁场事件，大约1100万年来一直影响着地球。