It has been noted above that the gravitational forces of both the moon and sun act upon the waters of the earth. Since the resultant or combined tidal force is also increased, the observed high tides are higher and low tides are lower than average. This means that the tidal range is greater at all locations which display a consecutive high and low water. Each force tends in part to counteract the other. In the tidal force envelope representing these combined forces, both maximum and minimum forces are reduced.
High tides are lower and low tides are higher than average.
The moon's gravitational attraction for the earth's waters will change in inverse proportion to the third power of the distance between the earth and moon, in accordance with the previously mentioned variation of Newton's Law of Gravitation. Both the Moon and the Earth revolve in elliptical orbits and the distances from their centers of attraction vary. This diagram also shows the possible coincidence of perigee with perihelion to produce tides of augmented range. When perigee, perihelion, and either the new or full moon occur at approximately the same time, considerably increased tidal ranges result. The Diurnal Inequality.