When the value of the angle between the direction of the sun and moon is close to 0 degrees, the moon appears as a thin crescent. As the angle increases, the moon appears as a larger crescent, then a half moon, and eventually a gibbous moon. When the angle reaches 180 degrees, the moon appears as a full moon.
The angle between the sun and moon determines the amount of the moon's illuminated side that is visible to Earth. A smaller angle corresponds to a smaller visible portion of the moon, resulting in a crescent shape. As the angle increases, more of the illuminated side becomes visible, transitioning from crescent to half moon. When the angle is 180 degrees, the entire illuminated side is visible, resulting in a full moon.
Overall, the appearance of the moon phase correlates with the value of the angle between the sun and moon.
In the Phase Simulator, click on the option labeled show angle (if not already done so)-which graphically displays the angle between the direction of the sun and moon. Now drag the moon around the sun to a variety of different locations and note the appearance of the Moon Phase. Describe how the value of the angle correlates with the appearance of the moon.
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