As a human being on planet earth, I think you would have had to live a very extraordinary life not to have noticed the monster white circle that graces our night sky. The moon has been a mythological pillar of many cultures, the subject of many stories, as well as being thought of as the cause of temporary insanity, depending on its phase. This is where the phrase "lunatic" comes from. Derived from the latin, "luna", meaning moon, people displaying signs of temporary insanity would be attributed to the full moon. The full moon is also the cause of humans transmogrifying into werewolves, in older folklore as well as current movie pop-culture. The phase of the moon is directly related to the pull of the ocean tide. And yet in our ever busying culture, we are usually blissfully unaware of the moon, where it is, or what phase it is in.
To begin lifting the veil, let's describe why the moon has phases. At almost any given time, the moon is being illuminated by sunlight. Since it is a sphere, only half of it can be illuminated, since there is only one light source, the sun. As onlookers from Earth, as the moon makes its round-earth traverse, we are able to see this half-illuminated and half-dark moon from many different angles. These are what are known as the phases. They are totally based on the fact that we are earthbound and in a specific position relative to the moon. Again, the moon is almost always half illuminated and half dark, the exception being an eclipse. So, this visual phase is almost entirely, in some sense, an illusion to the earthbound viewer. The moon phase is a powerful tool, because by simply looking in the sky, and identifying how the moon looks. You can tell where the moon is in relation to the earth and the sun.
Next, let's describe a few key words to get the jargon under control:
New Moon - This is when, from earth, the entire moon is in shadow.
Waning - This means to get smaller.
Waxing - This means to get larger.
Crescent - This is when the illuminated section of the moon is in the shape of a crescent. Generally, when the moon is less than half illuminated in view.
Gibbous - From the latin, meaning "hump". This is when the illuminated section of the moon is larger than half, giving a half + hump-like shape.
Quarter - NOT THE SHAPE OF THE MOON PHASE. This indicates when the moon has completed a quarters of it's journey from its New Moon position around the earth.
New Moon - Only the dark half of the moon is visible to the earthbound viewer.
Waxing Crescent - The moon begins to be illuminated, creating a larger and larger (waxing) crescent shape.
First Quarter - The moon has completed a quarter of it's traverse around the Earth. Half of the moon is illuminated and half is dark to the earthbound viewer. The left half is dark.
Waxing Gibbous - The moon's illuminated visible portion continues to grow (wax) greater than half, now in the shape of a gibbous.
Full Moon - 100% of the moon is illuminated from the earthbound viewer's perspective.
Waning Gibbous - From 100% illumination, the moon begins to show some darkness, in a gibbous shape.
Third Quarter - Three quarters of the traverse around the Earth, half of the moon is dark (right) and half of the moon is illuminated.
Waning Crescent- From half, the illumination continues to dwindle, in a crescent shape, growing ever smaller.
New Moon - Returning, only the dark half of the moon is visible to the earthbound viewer.
