The cyclical movement isn't perfect though. As we saw in QCJ, small changes are introduced with each revolution.

Each day may be a day, but it is still different from the day before.

And though the process may begin, these small changes have the ability to redirect the entire course it will take.

yesyes

it's like a rock rolling down a hill. As it picks up and drops debris, the surface of the rock changes slightly.

Although it's still picking up speed.