Tide

Tide

The rise and drop of sea levels caused by the gravitational force of the Moon.

Geography

Keywords

tide, ebb tide, flood tide, gravity, Moon, gravitation, Sun, sea, high tide, low tide, tsunami, neap tide, nature, geography

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Scenes

Narration

The gravity of the Moon, and to a lesser extent that of the Sun, are responsible for changes in the sea level on the Earth. The Moon attracts the water in the oceans and the seas, so water rises on the side of the Earth facing the Moon and forms a bulge of water.

Orbiting around a common center of mass, the Earth and the Moon form a "double planet". Since the Earth is much larger, the common center of mass lies in the interior of the Earth. On the other side of the Earth, opposite the common center of mass, the centrifugal force also pulls the oceans and the seas towards it, creating another bulge of water there.
Thus there are simultaneously two bulges of water on the Earth, which travel around the oceans and seas due to the rotation of the Moon around the Earth. In some areas, tides can change every six hours.

The highest level of water is called high tide, while the lowest level is low tide. The fall in water level from high tide to low tide is called ebb tide; the rise in water level, from low tide to high tide is called flood tide. The tides are also affected by the gravitational pull of the Sun, but to a lower extent.

At New Moon, when the Earth, Moon and Sun are aligned, the Sun reinforces the pull of the Moon and sea levels are higher than usual. This is called spring tide. When the Earth, Moon and Sun form a right angle, the Sun weakens the pull of the Moon, so high tide is lower than usual. This is called neap tide.

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