Question

lesson a3: the moon
student exercises - unit a earth, moon and sun - a3 the moon - 3 moon and sun
question 3a: what do you think the lines at the top and bottom of the moon represent?
you can also see the sun and the earth. notice the position of the three objects.
question 3b: why is the moon dark?
click the run time forward button. when the sun reaches the left edge of the screen, click the pause time forward button again to stop the time flow.
question 3c: why do we now begin to see part of the moon?
question 3d: based on your observations, does the moon give off its own light?

Explanation:

3a: Likely the terminator (boundary of light/dark on the Moon). 3b: Moon lacks own light; dark when not reflecting sunlight. 3c: Sun's position changes, illuminating part of the Moon. 3d: Moon reflects sunlight, doesn't emit its own.

Answer:

3a: The lines likely represent the terminator (the boundary between the illuminated and dark parts of the Moon).
3b: The Moon is dark because it does not produce its own light and is not reflecting sunlight at that position.
3c: We begin to see part of the Moon because the changing positions of the Sun, Earth, and Moon cause sunlight to illuminate a portion of the Moon's surface, which then reflects to Earth.
3d: No, the Moon does not give off its own light; it reflects light from the Sun.