Why is it night?

A photo from a hotel room in Las Vegas. Why is it night? Day and Night cycles are based on which parts of the earth the rays of light from the sun hit. At this particular time, the earth had rotated to a particular point where Las Vegas was on the side of the earth not illuminated by the Sun. There is no moon in this picture, but it was in the sky that night. The moon moves around the earth in an elliptical pattern while also revolving around it's own axis. As it moves around, only one side of the moon is visible to the earth and this determines what kind of moon there is. I think on this particular night, it was a waxing gibbous.