It's a bit like when you are travelling along in your car. The objects at the side of the road flashes by, but the the appearance of the mountains in the distant background hardly changes at all.
The animation opposite shows the effect with stars.
As the earth moves from its summer position to its winter position, the yellow star in the middle of the picture appears to move across the sky as shown by the blue arrow. The further it appears to move, the closer it is to us. Click on Reload or Refresh to repeat the animation. Click here for the maths.
Animation by S.Mack & Gif Movie Gear
