What are the Phases of the Moon?
The phases of the moon refer to the moon’s changing appearance during the course of a lunar month. A lunar month is the time taken by the moon to complete one revolution around the earth. A lunar month is of 27.3 days, but the earth’s simultaneous motion around the sun makes it seem as if the moon takes two days longer, around 29.5 days. The moon gets its illumination from the sun. The side facing the sun is the one lit up and the side facing away from the sun is in darkness. Only the bright portion of the moon is visible from earth. During a lunar cycle, as the moon revolves around the earth, the bright portion of the moon is seen at different angles from the earth. This makes it appear like the moon is changing its shape. Eight phases of the moon occur in a lunar cycle. They are New Moon, Crescent Moon, First Quarter Moon, Waxing Gibbous Moon, Full Moon, Waning Gibbous Moon, Last Quarter Moon, Crescent Moon and New Moon. The phases of the moon keep repeating in an endless cycle, but,
The Moon orbits Earth at an average distance of 382,400 kilometers. The lunar month is the 29.53 days it takes to go from one new moon to the next. During the lunar month, the Moon goes through all its phases. You can see the phases drawn in the image below. Just like the Earth, half of the Moon is lit by the Sun while the other half is in darkness. The phases we see result from the angle the Moon makes with the Sun as viewed from Earth. The diagram below on the right is one you typically see in books. Don’t let it confuse you. The images of the Moon show what you see the Moon look like from Earth when it is at given points in its orbit. It does not show which side of the Moon is lit by the Sun. The side lit by the Sun is always the side that is pointed toward the Sun, as seen in the diagram below on the left.
