Question

monday: why do stars appear to move across the night sky?

Explanation:

Step1: Earth's rotation

The Earth rotates on its axis.

Step2: Relative motion perception

We are on Earth. As Earth rotates, stars seem to move across the sky relative to our position.

Answer:

The stars appear to move across the night sky because the Earth rotates on its axis, causing a relative - motion perception from our position on Earth.