Crescent Moon
Written by Fraser Cain
A crescent moon occurs when the side of the Moon illuminated in sunlight is facing away from the Earth. We can see a sliver of sunlight on one side of the Moon, while the rest of the Moon is enshrouded in shadow.
We see a crescent moon just before or after the new Moon, when the Moon is perfectly lined up between the Sun and the Earth. To have a crescent moon; however, the Moon is to be slightly to the left or right of this line up geometry. We see most of the Moon in shadow, but a little bit in sunlight.
When the Moon is changing from a new moon to a full moon, the crescent moon is the first phase, followed by a quarter moon – when the Moon is half illuminated. This first quarter is known as a waxing crescent moon.
When the Moon is changing from a full moon back to a new moon, the crescent moon is the last phase after the last quarter Moon – it's known as a waning crescent moon.
The crescent moon is also a symbol that has been used Asia Minor by the ancient Turks, and then by the religion of Islam after that. Many Islamic nations use the crescent moon in their flags.
Here's an article on Universe Today that explains all the phases of the Moon.
Want to learn more about the phases of the Moon? The US Naval Observatory lists the times for various Moon phases. And here's a cool calculator.
You can listen to a very interesting podcast about the formation of the Moon from Astronomy Cast, Episode 17: Where Did the Moon Come From?
Filed under: Astronomy
