Yin and Yang are originally the sun turning to the back, the sun turning to the sun, and the sun turning to the back. China is located in the northern hemisphere, and the mountains and rivers are roughly east-west and cross each other. Shan Zhinan and the north of the water are Yang, so Shan Zhinan and the north of the water are Yang, and vice versa. "Twenty-eight years of Xi Gong": "The north water is Yang, and the south water is Yang." Xu Shen's "Shuo Wen Jie Zi": "Yin, dark also; South of the water, north of the mountain. " Li Jifu further pointed out in Yuanhe County Records: "The mountains are sunny in the south and cloudy in the north; The water in the north is yang, and the water in the south is yin. Place names named after Yin or Yang reflect their geographical orientation, such as Huayin in the north of Huashan, Hengyang in the south of Hengshan, Jiangyin in the south of the Yangtze River, Huaiyin in in the south of Huaishui, Hanyang in the north of Hanshui and Luoyang in the north of Luoshui. ...

China lies in the northern hemisphere. From our point of view, the sun will rise in the east, cross the south and finally set in the west. The south of the mountain is sunny slope, and the north of the mountain is backlit slope. There must be more sunshine in the south than in the north, so the south of the mountain is called Yang and the north of the mountain is called Yin.

Because the topography of water in China is high in the northwest and gradually low in the southeast, rivers often flow to the southeast, and the south bank is easily eroded by river water, forming a situation that the south is wet and the north is dry, so the water in the north is called Yang and the water in the south is called Yin.

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