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

要知道，快速眼动睡眠是周性生的。

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.

瑞士历史学家让-夏尔·西斯蒙是识别周性经济生的学者，但揭示其周性形式的是后来的经济学家、法国人夏尔·多尼耶（1786年至1862年）的工作。

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

些研究暗示，这可能是周性生的磁场事件，大约1100万年来直影响着地球。