So I was watching the Sun set the other night, and I noticed that the Sun appeared to accelerate into the horizon. If the Earth rotates at a constant angular speed, how could this be? I was thinking about swinging a ball on a string vertically, and how the ball would have different points of maximum acceleration along its path due to the different forces acting on it. But the Sun only has a single radial force that wouldn't vary thoughout its path (that is, if the Earth was taken as a stationary frame). Can anyone explain this?