Tides

What causes tides?

The alternating rise and fall in sea level with respect to the land, produced by the gravitational attraction of the moon and the sun is called as tides.Tides are created because the Earth and the moon are attracted towards each other.

The force of attraction is given by

F=GM₁M₂/R²,

where G is the universal gravitational constant given by 6.67x10^-11 Nm² /kg²,

M1 is the mass of the Earth,

M2 is the mass of the moon and

R is the distance between the Earth and the moon.

                Due to this gravitational force the moon tries to pull everything on the Earth to bring it closer. The Earth holds everything onto it, but water being a fluid the Earth cannot hold it and the moon is able to pull it. In a day there occur two high tides and two low tides. The gap between two tides is around 12 hours 25 minutes.

Tides are periodic rise and fall of water bodies. Winds and currents move the surface water causing waves. Ocean levels keep on changing daily due to the interaction of the Sun, moon and the Earth interact. As the moon travels around the Earth and both Earth and moon together travel around the Sun, the combined gravitational forces cause the world's oceans to rise and fall. Due to the Earth’s rotation during these interactions, there is an occurrence of two tides in a day.

There are two different types of tides-

1)      Spring tides- During full moon or new moon, the gravitational attraction of the Sun and moon are combined. During this time, the high tides are very high and low tides are very low. Such tides are known as spring tides. Both the Sun and the moon contribute to the tides.

2)      Neap tides- At the time of the quarter phases of the moon, the Sun and the moon are at right angles and thus, the bulges due to them cancel each other. Due to this the difference between high tides and low tides is usually small and such tides are known as neap tides.

Some facts about tides:

·         The Sun’s gravitational force also produces tides, but due to the large distance between the Earth and the Sun, the forces are smaller as compared to the moon and hence the effects are greatly decreased.

·         The sun's gravitational force on the earth is only 46 percent that of the moon. That is why the moon has more influence on the formation of tides.

·         The gravitational force of the moon is one ten-millionth that of earth, but still tides are formed due to other forces such as the earth's centrifugal force created by its spin.

·         Tides are not caused by the direct pull of the moon’s gravity. The moon pulls the water upwards while the Earth pulls it downwards which causes the tides.

·         Spring tides and neap tide levels are about 20% higher or lower than average.

·         In the deep ocean, the difference in tides is usually less than 1.6 feet.

·         The surf grows when it approaches a beach, and the tide increases.

·         The highest tides in the world are at the Bay of Fundy in Nova Scotia, Canada. They have a range of 44.6 feet.

·         The moon rotating about the Earth is not at the same place at the same time each day. So each day, the times for high tides and low tides change by about 50 minutes.

-Article done by MAULIK JOSHI