The Sun doesn't move across the surface of anything. It's a giant ball of burning gas in space.

What you might be thinking of is the apparent movement of the Sun across the sky. This is caused by the Earth's rotation on its axis.

Here's a breakdown:

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

* Apparent Sun Movement: As the Earth rotates, it appears to us that the Sun is moving across the sky from east to west. This is just an illusion caused by our perspective from Earth.

So, there's no actual speed at which the Sun moves across the surface of anything. It's the Earth's rotation that creates the illusion of the Sun moving across the sky.