Question: What does waxing and waning mean?
Answer: The term waxing means to increase. The term waning means to decrease.
Question: When viewed from the Northern Hemisphere, how can you determine if the moon is waxing or waning?
The moon phases in the diagram show an increase in the lighted area from day 1 to day 7. This means the moon is waxing.
The terminator, which is the line between the dark and lighted parts of the Moon, moves from West to East (right to left) in the Northern Hemisphere. Looking at day one’s moon phase, you can predict that the Moon is waxing because the terminator line will be farther to the east the next day. It appears that the terminator is attached to the lighted part and is pulling it over the dark surface.
The term waning means to decrease. The Moon photos to the left are examples of a waning moon. From Nov. 8 to Nov. 12, the size of the lighted surface of the Moon decreases–gets smaller. The terminator line is moving westward, but this time it seems to be attached to the dark, which it is pulling over the lighted part of the Moon’s surface.
Challenge:
Create a model that represents the movement of the terminator during one lunar month from one new moon to the next new moon.
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