Throughout each month the moon will change from a crescent shape to a full moon. The stages in between are called phases. After seven days the moon will change from a crescent to a half moon. For the next seven days the moon will change from being a half moon to a full moon. The reason why it has full and half moons depends on how the sunlight reflects off of the surface of the moon and how much of it we can see. The shadow on the moon always goes from east to west. The line that divides the part we can see from the dark part is called the terminator.

Animation by Stephen Gray using photos © James Funkhouser.

 

FUN FACT

Did you know that half of the moon is always lit?