Yang is the warming cycle, Yin is the cooling cycle.
The movement of light and dark throughout a twenty-four hour period is the motion of Yin and Yang expanding and contracting, flowing, one into the other in an endless dance.
Observing the small nuances of these changes is a simple and profound learning experience. Particularly observe the peak changes of sunrise, noon, sunset, and midnight. Explore with every sense the changes in light, temperature, activity, sound, smell, and energy. Even if you are in a busy city, just pause and notice.
Leave the lights off and watch the day pass into night, or the light returning in the morning. Observation of Nature is how the ancients learned the theory of Yin and Yang. We have that same opportunity every minute of the day and night.
Please share what you notice in the comment box below, so we can keep learning from each other.