|Waves at the beach of Lisabon|
Tides are mainly due to the difference in attraction exerted by the moon on parts of the earth. We can divide the earth into three areas: areas closer to the moon has the strongest attraction, area's far from the moon are turned away, the weakest, and then there are the parts that lie between here. If these three areas were not subject to the influence of the moon, there would be a water storage occur on the two opposing portions. But because the spike-rotates, move this mountain water, also called flood mountains, is an apparent movement of the Moon around the Earth. The sun exerts an influence here, but because the sun is much farther from Earth than the moon, this influence is much less. When the sun, moon and earth are in line, the sun strengthens the tides caused by the cooperation between the sun and the moon. In this case we speak of spring. The flood has a maximum height. In the other case, there is slack water. This occurs when the sun is perpendicular to the line to the moon at a minimum height. The sun does the tidal movement against it.