From the 15th to the 1st day of the lunar calendar, the area of ??the side of the moon illuminated by the sun that we see will be .

Unless there is a lunar eclipse, half of the moon is always illuminated. This is just because the position of the moon relative to the earth changes, resulting in a lunar eclipse. The first day of the lunar month is the new moon, and the fifteenth day is the full moon. The moon phase changes from first quarter to full moon. The full moon changes, and the illuminated part we see becomes larger.

On the first day of the lunar month, the sun - moon - earth is arranged, so that at night on the earth, the moon on the other side of the earth cannot be seen.

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At fifteen o'clock, the sun - earth - moon are arranged, so that at night on the earth, you can see the entire moon illuminated by the sun.

This illustrates that in the entire three-dimensional space Under the sun, the sun's rays can reach the moon without being blocked by the earth and should not be limited to a flat surface.