There are four different tides, depending upon the position of the sun and moon in relation to the earth. When the sun and moon are in direct line with the earth, they exert their greatest gravitational force, causing abnormally high or spring tides. When the sun, moon, and earth are at right angles to each other, gravitational force is weak casing abnormally, low or neap tides. between these tow ext reams are high, or perigee, tides when the moon is closest to the earth and low, or apogee tides when the moon is farthest from the earth