For instance, let me reword this question: How does a cat go from feet-up to feet-down in a falling reference frame, without violating the conservation of angular momentum?
所以，我来换一种问法： 为什么猫在一个下降坐标系中， 可以将四脚朝天的姿态调整为四脚着地， 而又不违反角动量守恒呢？