If you go to the shore in the early morning and stay there all day, you can observe an interesting phenomenon. Leave your towel in the sand about 30 feet from the water, and in a few hours, you’ll find that the surf is splashing nearby or has already swept it off into the deep. If you keep watching, you’ll notice that after a certain period of time, the water begins to recede and the towel falls back farther than it was even at the beginning of your observation. This is due to gradual changes in the water level, called high tide and low tide. The more gradual the shore’s slope, the more visible these changes are. 

Many of you have probably heard that the tide is connected to the Moon. It’s true: our planet’s satellite unevenly affects the World Ocean with the strength of its gravitational pull — the closer to the Moon, the stronger the effect. Let’s recall the formula for the force of gravity. It is inversely proportional to the square of the distance between the objects in question. When dealing with the distance to the Moon, such distances as the radius and diameter of the Earth are important. Therefore, due to the differences in force, water is “distorted” into bulges.