Earth rotates on its axis once every 24 hours! This causes us to experience day and night on Earth. Because Earth is rotating toward and away from the Sun constantly, we have what is called the Day/Night cycle. This means that day and night always happen in a pattern that we can predict. Think about it, have you EVER had a day that had no night? Or have you ever NOT had daytime? If you answered no to those questions, you are CORRECT!
Earth's rotation also causes the Sun to LOOK like it is moving across the sky. Of course, the Sun is NOT moving. It only looks that way. Instead, Earth is rotating toward and away from the Sun each and every day!
We can prove that Earth rotates on its axis! There are three great pieces of evidence that prove that Earth is actually rotating! The first is the Day/Night Cycle. The fact that we have day and night, and that it is a predictable pattern, is proof that Earth is spinning. The second piece of evidence is the apparent (this means "it looks like") movement of the Sun. Since the Sun looks like it is moving across our sky, and it goes the same direction all the time, we know that Earth is rotating. Finally, the last piece of evidence is the fact that shadows change throughout the day! The shadows change because the position of the Sun changes in the sky!