Collected Illustrations of the Three Realms, Volume 4: Astronomy

Discussion on Eclipses of the Sun and Moon (Continued)

Where the light of the Sun and Moon does not reach is called the Dark Void. original: "àn xū" (暗虛). Traditional Chinese astronomy used this term to describe the region of darkness directly opposite the Sun where lunar eclipses occur. When the Dark Void encounters the Moon, a lunar eclipse occurs; when it encounters a star, that star vanishes. Currently, astronomers original: "lìjiā" (曆家), literally "calendar experts," who were the professional astronomers of the imperial court. observe that when the Full Moon travels along the Ecliptic, original: "huángdào" (黃道), the apparent path of the Sun across the sky. it encounters this Dark Void. Because the encounter with the Dark Void can be at the edge or the center, and can be shallow or deep, lunar eclipses vary in their direction—occurring to the north or south—and in their magnitude.

In my assessment, the theory of the Dark Void cannot be easily disputed. However, if one says that its size is only as large as the Sun, I fear its size is actually greater than that. Consider that some lunar eclipses last for two or three double-hours. original: "shíchén" (時辰). One traditional Chinese double-hour equals two modern hours. If the Dark Void were only the size of the Sun, how could an eclipse last so long?

Today, the diagrams of the Dark Void produced by astronomers show that it is large enough to contain three or four Moon-bodies. By observing the stages of first contact, original: "chūshí" (初食), the start of the eclipse. totality, original: "shíjì" (食既), when the Moon is first fully covered. and maximum eclipse, original: "shíshèn" (食甚), the point of deepest coverage. it is evident that the size of the Dark Void is not merely equal to the Sun, but far exceeds it.

However, I did not know why this Dark Void existed exactly at the point of opposition to the Sun. I humbly speculate, based on my own reasoning, that the Dark Void is simply the shadow of the Earth, and nothing else. Since the Earth sits at the center of the heavens and the Sun travels across the sky, even though the heavens are vast and the Earth is small, the Earth still blocks a portion of the Sun's light. The sunlight scatters around the four [sides of the Earth...]