So, you reinforce the pig for walking forward and you punish the pig for walking backward.

那你就对这头猪向前走的行为给予强化,如果它向后退，你就惩罚它。

耶鲁公开课 - 心理学导论课程节选

And now since it's reversible, we can run it forward or backward.

因为它是可逆的，所以可以正方向运行。

麻省理工公开课 - 热力学与动力学课程节选

If that's all it knows, then in that scenario there is no building or anything else; it continues a trajectory both forward in time and backward in time, and it says that whatever seconds, one second before you set your clock to 0, it would've been on the ground.

如果是这样,在那种模式下,没有楼房或者别的什么,物体的运动轨迹可以沿时间可以向后延伸,也可以向前延伸,不管时间取什么值,在零点前一秒时,物体就在地面上

耶鲁公开课 - 基础物理课程节选