Why does the moon appear when the sun goes down?

The sun is shining all the time. The presence of the moon doesn't mean that the sun stops shining. In fact, when you see the moon, you are seeing sunlight reflecting off the moon's surface. You may wonder how it is that you can see both the sun and moon in the sky at the same time. It's just a matter of geometry. Sometimes the sun moon and earth are lined up in such a way that we see the sun and moon in the sky. You will notice that when this happens, the moon is never full.