Pour water into a glass.
The water quickly comes to rest. In stillness.
It seems that nothing is moving.
It seems that there is no change.
But water molecules are always moving about.
Although they are evenly distributed in the system (the glass of water), they do not stop moving.
The water is still because there is no net change in the system – the molecules are equally spread.
The water (as a whole) appears motionless and still.
This stillness is known as dynamic equilibrium – constant change within no net change.
It is yang hidden in yin.