Because we find in that plane, when objects are left at what you think is at rest with no external agency acting on them, they all slide backwards towards the rear end of the plane.

因为我们发现,在飞机上,当物体掉在地上,你认为它不受外力作用,应该保持静止时,它却朝着飞机的尾部滚去

耶鲁公开课 - 基础物理课程节选