* The sun's brightness: The sun is so incredibly bright that it washes out the light from stars during the day. Even though stars are still there, we simply can't see them because the sun's light overwhelms them.
* Earth's rotation: As the Earth rotates, the sun appears to rise in the east and set in the west. This rotation also causes the stars to appear to move across the sky, but much more slowly.
* The illusion: Because we only see stars at night, and the sun rises in the east, it might seem like they "appear" with the sunrise. However, the stars have been there all along, hidden by the sun's light.
So, the real reason stars appear at night is because the sun is below the horizon, allowing their light to be seen.
