The daily rise and fall of water level in the oceans is called a tide. You can see it on the shore of the ocean.The gravitational pull of the moon and sun and the centrifugal force created due to the rotation of the earth causes the tides.The gravitational pull bulges out the water in an ocean in the direction of the moon.The gravity of the sun is much more than the moon, but as the sun is far away from earth, therefore its effect of gravity is less than that of the moon’s gravity on the water of the ocean.The sun’s gravitational force on the earth is only 46% that of the moon, which makes the moon the only important factor for the creation of tides.
Lunar Tides The moon and the earth exert gravitational pull on each other. The moon causes the water of the oceans on both sides i.e., closest to the moon and farthest from the moon and creates tides. The reason for the closest side is that, this side is close to the moon hence more gravitational pull of the moon bulges the water. The reasons for the farthest side are: 1. It is farther and hence weak gravitational forces on this side. 2. The rotation of the earth around its axis creates centrifugal force which acts against gravity as well as pulls the water of the ocean away from the moon and creates bulges.Therefore the bulge on the farthest side is due to centrifugal force.
As the moon orbits our planet and as the Earth rotates, the bulge also moves.Since the earth is rotating around its axis completing one rotation in a day therefore, each day, there are two high tides and two low tides. The ocean is constantly moving from high tide to low tide, and then back to high tide.
Spring Tides
They occur when the moon, earth and sun are in one line. Spring tides occur during the full moon and the new moon i.e two times a lunar month. when these three bodies are in one line,the solar tide has an additive effect on the lunar tide, creating extra high and very love tides.these tides are strong tides.
Neap Tides
Neap tides occur during the 1st quarter moon and 3rd quarter moon i.e two times in a lunar month. During the first quarter moon or third quarter moon (sometimes half moon), the sun and moon are at right angles (90 degrees ) causing the bulges to cancel each other.The result is a smaller difference between high and low tides and is known as a neap tide. Neap tides are especially weak tides. They occur when the gravitational forces of the Moon and the Sun are perpendicular to one another (with respect to the Earth). In this situation, despite its greater distance, the Sun’s mass allows It to exert some gravitational force on the oceans that it can negate some of the effects of the Moon’s pull.
Summary: The gravitational force of the moon and the earth’s rotation about its axis which creates centrifugal force are the two important factors for bulging the water of oceans and seas and creating all types of tides.
Zia Ahmed Khan, email: khanziaahmed50@gmail.com
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