In an old Western movie, we notice that a stagecoach wheel appears to be moving backwards at $5^{\circ}$ per frame, even though the stagecoach is moving forward.
To what is this effect due? What is the true situation?

Question

In an old Western movie, we notice that a stagecoach wheel appears to be moving backwards at $5^{\circ}$ per frame, even though the stagecoach is moving forward. 
To what is this effect due? What is the true situation?

Quizplus · Accepted Answer

The Answer of In an old Western movie, we notice that a stagecoach wheel appears to be moving backwards at $5^{\circ}$ per frame, even though the stagecoach is moving forward. 
To what is this effect due? What is the true situation?

In an Old Western Movie, We Notice That a Stagecoach 5∘5^{\circ}5∘

In an Old Western Movie, We Notice That a Stagecoach $5^{\circ}$