Moon causes waves

The gravitational force of attraction between two massive bodies is larger for larger masses and increases as the distance between them decreases. Tides result from the difference in the moon's gravitational force between two opposite sides of the earth. The side nearer to the moon is pulled with greater force than the center of the earth while the side farther from it is pulled with less force. When the centrifugal force, which is equal and opposite of the gravitational force on the center, is subtracted, the result is two forces pulling away from the center. This mostly affects the oceans which are fluid and therefore easily deformed by this tidal effect resulting in two bulges on opposite sides of the earth in line with the moon.