Daily Yin-Yang Time Model
Beyond the annual cycle created by the Earth’s revolution, the Yin-Yang model most directly connected with everyday life is the daily Yin-Yang time model produced by the Earth’s rotation. With a 24-hour period, this model marks the energetic rise, peak, decline, and concealment of yang qi over the course of a day. The core first-principles idea is the strong entrainment of biological rhythms by the local rotational light cycle. The daily waxing and waning of yang qi is, in essence, treated as the nonlinear fluctuation of local solar-radiation intensity. When 24-hour dark-field radiation data collected over thirteen months are aggressively averaged and visualized, the resulting pattern is likewise described as resembling a highly regular Taiji form. Such external fluctuations of light and heat are taken to govern the circulation of defensive qi (wei qi) and the secretion of melatonin in terrestrial mammals. Consider jet lag after international travel. When the body flies from one time zone to another, its internal Yin-Yang model becomes misaligned with the external spatiotemporal environment. The best ally for readjustment, in this account, is not medication but the local Sun on that day. Direct exposure to local sunlight helps the body’s daily Yin-Yang model realign as quickly as possible with the local rotational light cycle. The reason this can help is that the body is still synchronized to the solar cycle of the departure location, creating a phase difference in the circulation of wei qi relative to the destination—the phenomenon commonly called jet lag.
