The positions of planets change in relation to background stars because planets orbit the Sun, while stars are much further away and appear relatively stationary from Earth's perspective.

Here's a breakdown:

* Planets orbit the Sun: Planets are much closer to Earth than stars. As they revolve around the Sun, their position in the sky shifts relative to the distant, seemingly fixed stars.

* Stars are very far away: Stars are unimaginably vast distances from Earth. Their movement is incredibly slow from our point of view, so they appear almost motionless.

* Earth's perspective: From Earth, we observe the planets against the backdrop of these distant stars. Because planets are closer and moving, they appear to "wander" across the sky.

This is why planets were historically called "wandering stars." Their movement against the fixed background of stars was noticeable to ancient astronomers.