Moon phases vary slightly as the moon rotates around the earth and the appearance of the moon changes, although the moon itself remains the same. Whether you're an amateur stargazer or follow your daily horoscope in astrology, knowing and recognising the phases of the moon can be highly useful.
The rotation of the moon around the earth makes it seem like it appears and disappears at various times of the month. This is caused by the different amounts of the moon's surface that is reflecting light from the sun. There is a set pattern of four major moon phases. The time between two full moons is roughly 29.5 days, a lunar month.
The time of month when there appears to be no moon in the night sky is called a new moon. The side of the moon that is facing the earth is not lit by the sun, making the moon look as though it has disappeared. This is caused by the sun and the moon being on the same side of the earth. There are times when the earth is blocking the light from the sun and casts its own shadow across the moon and causes a lunar eclipse.
Waxing means "to grow." During this phase, the moon appears to be growing from a new moon, or no moon, towards a full moon. The surface of the moon turns more and more towards the sun, giving the illusion of getting "bigger."
When the moon lies directly on the opposite side of the earth from the sun and appears to be completely illuminated, it is called a full moon. At this point, the moon appears completely round, fully lit and larger than usual.
When the right side of the moon appears dark and the brighter part seems to be disappearing, the moon is in its waning phase. Waning means "to shrink." Once the moon totally disappears, it has entered the new moon phase and the moon phase begins to repeat itself.
Sometimes there are two full moons that appear within the same calendar month. The second full moon is called a blue moon, hence, the saying, "once in a blue moon." Since seasons are only three months long, which divides the year into four parts, a blue moon also occurs when a season hosts more than three full moons. There are occasions when the moon does appear blue in colour due to smoke or dust in the air. These two events have nothing in common.