Tide between springs and neaps. The changing distance separating the Moon and Earth also affects tide heights. When the Moon is closest, at perigee, the range increases, and when it is at apogee, the range shrinks. Every lunations (the full cycles from full moon to new to full), perigee coincides with either a new or full moon causing perigean spring tides with the largest "tidal range". Even at its most powerful this force is still weak, causing tidal differences of inches at most. These include solar gravitational effects, the obliquity (tilt) of the Earth's Equator and rotational axis, the inclination of
Chinese sun and moon mirrors moon-mirrors and beliefs that certain marine animals waxed and waned in correspondence with the moon. For example, the (c. 3rd century BCE) "Guanzi" says, The virtue of a ruler is what all the people obey, just as the moon is the root and fount of all Yin things. So at full moon, shellfish ["bangge" 蚌蛤] are fleshy, and all that is Yin abounds. When the moon has waned, the shellfish are empty and Yin things weak. When the moon appears in the heavens all Yin things are influenced right down to the depths of the sea. So the sage lets