Tai Chi Tu. BASICS OF “YIN” and “YANG”. SEE http://en.wikipedia.org/wiki/Yin_and_yang. The nature of yin–yang. Yin is characterized as slow, soft, yielding, diffuse, cold, wet, and receptive; and is associated with water, earth, the moon, female and nighttime.
It falls to the ground
“For every action there is an equal and opposite reaction.” (Mathematika)