In ancient times, how did our scholars view the various changes in the phases of the moon?

Sometimes the moon is full, sometimes it is short, and it is always changing regularly. People see such changes every day, but they don't always know the reason for it. As early as more than 1800 years ago, China's astronomer Zhang Heng in the Eastern Han Dynasty believed that the moon itself does not emit light, and that its light is the light reflected from the sun's illumination. Song Dynasty scholar Shen Kuo further pointed out that the shape of the moon like a projectile, the sun shines only to send out light: at the beginning, the sun in the moon next to the light from the side of it, we see "the moon as a hook"; after the sun gradually away from the far, the sunlight slanting, the moon phase is also slowly "full "up. Shen Kuo also used a half of the ball coated with white powder to do experiments: from the side, the powder seems to be a curved hook; from the front, it is a circle.