Ying Yang

In Chinese philosophy, the concept of yin yang (often referred to in the west as yin and yang) is used to describe how polar or seemingly contrary forces are interconnected and interdependent in the natural world, and how they give rise to each other in turn. The concept lies at the heart of many branches of classical Chinese science and philosophy, as well as being a primary guideline of traditional Chinese medicine, and a central principle of different forms of Chinese martial arts and exercise, such as baguazhang, taijiquan, and qigong and of I Ching divination. Many natural dualities — e.g. dark and light, female and male, low and high, cold and hot — are viewed in Chinese thought as manifestations of yin and yang (respectively).

A symbol combining the sun (top) and moon (bottom). It's easy for people to understand the philosophy by talking about the sun (Yang), moon (Yin) and universe. After observing the universe, ancient Chinese found that the universe is changing every day. Although it changes easily every day, it also has seasonal and annual cycles.

By observing the sky, recording the Dipper's positions and watching the shadow of the Sun from an 8-foot (Chinese measurement) pole, ancient Chinese determined the four directions. The direction of sunrise is the East; the direction of sunset is the West; the direction of the shortest shadow is the South and the direction of the longest shadow is the North. At night, the direction of the Polaris star is the North.

They noticed the seasonal changes. When the Dipper points to the East, it's spring; when the Dipper points to the South, it's summer; when the Dipper points to the West, it's fall; when the Dipper points to the North, it's winter.

When observing the cycle of the Sun, ancient Chinese simply used a pole about 8 feet long, posted at right angles to the ground and recorded positions of the shadow. Then they found the length of a year is around 365.25 days. They even divided the year's cycle into 24 Segments, including the Vernal Equinox, Autumnal Equinox, Summer Solstice and Winter Solstice, using the sunrise and Dipper positions.

They used six concentric circles, marked the 24-Segment points, divided the circles into 24 sectors and recorded the length of shadow every day. The shortest shadow is found on the day of Summer Solstice. The longest shadow is found on the day of Winter Solstice. After connecting each lines and dimming Yin Part from Summer Solstice to Winter Solstice, the Sun chart looks like below. The ecliptic angle 23 26' 19'' of the Earth can be seen in this chart.