台湾籍旅美老师今天交给我们的句子是：
With gravity, happy to pull its center of mass even more off balance. And the more off balance, it is the more gravity pulls in too! Physicist calls this kind of tipping an... Inverted Pendulum.
因为地心引力的关系，一失去重心就会倒下，重心越倾斜，地心引力的作用就越强烈，物理学家称这种现象为 倒单摆作用。
