SCIENCE20 - The Phases of the Moon
This science blog is about the phases of the Moon. Night after night we see the Moon take different shapes in the sky. These different shapes are called the phases of the Moon. How Moon phases occur, and how they are associated with eclipses of the Sun and the Moon, is somewhat complex. I took on this scientific subject as a challenge to try to explain it coherently so that I understood it (always my first goal), and so that nontechnical readers would appreciate the details of these lunar phenomena. I will leave it to the reader to decide if I was successful. First, I will talk about the basic orbital geometry of the Sun-Earth-Moon system that produces the phases of the Moon. Then I will identify the eight phases of the Moon, when they occur, and what causes them. Next, I will talk about how lunar phases are related to eclipses of the Sun and Moon. I will conclude by noting how the phases of the Moon affect life on Earth. I will li...