The Origin of Eight Trigrams: Explaining the Mechanism of Soil Response to Temperature Change

The Eight Trigrams has held a high position in the Eastern culture, but its origin of has been a mystery for thousands of years, thus it has not yet entered the scientific system. This research reveals the possible origin of the Eight Trigrams and the purpose of drawing the hexagrams. Research has shown that due to changes in the solar radiation there exist annual and diurnal soil temperature variable zones (STVZs). The heat conducts and interactions between the double-layer also form two different statuses of warming and cooling. In this paper the hydrometeorological factors such as temperature, relative humidity, absolute humidity and earth-air pressure were monitored or calculated in the STVZs. If the anural/diurnal STVZ is divided into three levels, and we associate soil cooling processes (Yin) with “--” and warming processes (Yang) with “—”. It is not hard to find that the distribution of soil status in soil profile at different times and locations clearly reflects the soil response to temperature change and reveals movement mechanism of earth-air and water. Furthermore, this model can be seen to be the source of the Eight Trigrams in the Yi-jing. The double-layer structure of the soil constitutes the foundation of the double trigrams. The Yin and Yang processes both form the primary driving force for phreatic water moves upward. Fu Xi invented the method of hou-qi, in which the monitoring of earth-air pressure in the closed system and applying Yin-Yang to draw Eight Trigrams and analysis of spatiotemporal status changes in the soil, which was then used to enact a calendar used as a guide to time for farming usage. The Yin-Yang and Eight Trigrams perfectly explain the response of earth-air to solar terms and mechanisms of water vertical cycle on daily/yearly timescales.