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Diagram of the Two Rites

This diagram, titled 'Er Yi Tu' (Diagram of the Two Rites), originates from the Ming dynasty encyclopedia Sancai Tuhui. It illustrates the celestial sphere ('Heaven') surrounding the central mountains ('Earth'). The lines indicate the paths of the sun at different times of the year.

Labels on the left (top to bottom):
North Pole
Summer Solstice
Spring and Autumn Equinoxes
Winter Solstice
South Pole

Labels on the right (top to bottom):
Winter Solstice
Spring and Autumn Equinoxes
Summer Solstice

The Path of the Sun and the Changing Seasons

The Middle Path Zhonglu: The celestial equator, or the sun's path during the equinoxes is situated ninety-one and a half degrees and a fraction away from both the North and South Poles. On the day of the Spring Equinox Chunfen: One of the 24 solar terms, marking the moment the sun crosses the celestial equator, the sun travels along this Middle Path. From the Spring Equinox until the Summer Solstice, the sun gradually moves toward the North Path Beilu: The sun's northernmost track, corresponding to the Tropic of Cancer; the Summer Solstice marks the sun's trajectory at this northern limit.

From the Summer Solstice until the Autumn Equinox, the sun turns back from the North Path toward the Middle Path; the Autumn Equinox marks the sun's trajectory upon returning to the center. From the Autumn Equinox until the Winter Solstice, the sun gradually moves toward the South Path Nanlu: The sun's southernmost track, corresponding to the Tropic of Capricorn; the Winter Solstice marks the sun's trajectory at this southern limit. From the Winter Solstice back to the Spring Equinox, the sun turns from the South Path and returns once more to the Middle Path.

Traditional Chinese astronomy divided the sky into "paths" or "circuits" to explain the sun's shifting position. The "Middle Path" equates to the Equator, while the North and South paths represent the sun's position at the solstices.

The varying length of the days—long or short—is due to the relative rising and falling of the Earth This refers to the traditional Chinese cosmological view where the perceived height of the sun relative to the horizon (the "rising and falling" of Earth's position in the celestial sphere) dictates the duration of daylight..