The sun doesn't actually move across the sky. It's the Earth's rotation that makes it *appear* as if the sun is moving.

Here's why:

* Earth's Rotation: Our planet spins on its axis, completing one full rotation approximately every 24 hours. This rotation is what causes day and night.

* Our Perspective: As the Earth rotates, we, as observers on its surface, experience the sun's position changing relative to us. Since we are moving with the Earth, it seems like the sun is moving across the sky.

* The Illusion: The sun is so far away that its apparent movement is just a result of our changing perspective as the Earth spins. Think of it like watching a distant car drive by – it appears to move across your field of vision, even though you are the one who is stationary.

In reality, the sun is stationary, and it's the Earth's spinning that creates the illusion of the sun's movement.