As most people know that there is a twice-daily occurrence with two high tides and two low tides taking place within a single 24-hour period. The role played by the moon (primarily) and the sun (secondarily) was not widely recognized until Sir Isaac Newtown proposed his theory on the gravitational pull of celestial bodies. Although factors such as the shape of the coastline, meteorological conditions, and the rotation of the Earth all act upon the oceans’ waters and affect the ultimate flow of the tides when they reach land, by far the most influential element is the moon. The gravitational attraction between the moon and the Earth’s waters is quite strong, and the tides respond to the moon’s every movement. It acts like an invisible hand that sets the waters into motion. Essentially, wherever the moon is in its orbit around the Earth, seawater tends to “pile up”, like iron filings under a strong magnet. The pile of water remains in place directly under the moon as the Earth rotates through its daily cycle. Of course, as the Earth spins, the relatively stationary pile of water under the moon eventually comes into contact with the continents. This is what produced a high tide. The heights of the tides vary through the cycle of the lunar month. During a New moon, for example, the sun and the moon are arrayed in a line on the same side of the Earth, the gravitational force of the two is added together and the highest high tides of the month occur, called spring tides. When the sun, the moon, and the Earth are arranged in a triangular configuration, the pull of the two celestial bodies is somehow offset, causing the most moderate tides of the month, called neap tides. Some have proposed building power generating plants to capture the energy of the oceans in the same way that the hydroelectric plants have been used to tap river power.