Question

the sun appears to move east to west in the sky.why ?

Answer 1

Because the Earth moves from west to east so we can see the Sun moving from east to west.

Answer 2

For the moment, let us just think about one motion - - Earth's spin (or rotation) on its axis. Earth rotates or spins toward the east, and that's why the Sun, Moon, planets, and stars all rise in the east and make their way westward across the sky.