China lies in the northern hemisphere. From our point of view, the sun will rise in the east and finally set from the west through the south. The south of the mountain is sunlight, and the north of the mountain is backlight. 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.
In ancient times, "Yin" refers to mountain north and water south, and "Yang" refers to mountain south and water north. For example, Huaiyin is south of Huaihe River, Hanyang is north of Hanshui River and Huayang is south of Huashan Mountain. Therefore, ancient geography has a set of theories to divide yin and yang, in which the "yin" of mountains and rivers refers to the north of mountains and the south of water;
The yin and yang attributes of things and phenomena are divided according to the nature, dynamics, position, development trend and other factors of things and phenomena that are interrelated in nature or within the same thing. Generally speaking, anyone who is hardworking, extroverted, progressive, enthusiastic, cheerful and excited belongs to Yang; The one who is relatively quiet, defensive, healthy, cold, depressed and restrained belongs to Yin. The yin and yang attributes of things and phenomena.
Su Wen's Theory of Yin and Yang: "Fire and water are also images of Yin and Yang". Through long-term observation of natural phenomena, the ancients believed that the contradiction between fire and water was the most prominent and typical, and its characteristics were the most representative of yin and yang. Because water is cold and wet, it can represent negative things and phenomena; Fire is warm and inflammatory, and can represent positive things and phenomena. Understanding the concept of yin and yang with the natural characteristics of fire and water can play a role in simplifying the complex.