AGE OF EARTH

3- ON THE BASIS OF TIDAL FORCE OF THE MOON

        The age of the earth based on tidal force of the moon is calculated in a variety of ways.First method - It is commonly believed that the moon was originated from the earth because it is earth's satellite as the moon revolve around the earth. If this is so, the moon might have been very close to the earth at the time of it's birth from the earth and the tidal friction of the moon might have been maximum. With the passage of time moon gradually moved away from the earth and hence the tidal friction of the moon also gradually decreased. The age of the moon and ultimately the age of the earth is calculated on the basis of the rate of the decrease of the tidal friction of the moon. The scientists have calculated the age of the earth, on this basis, as 4000 million (4 billion) years.

Second method -It is believed that the rotational force of the earth is reduced due to tidal friction of the moon. In other words, the time of the rotation of the earth increases( due to decrease in speed of earth's rotation) due to tidal friction of the moon. The , on the basis of the calculation of the tidal fiction of the moon and the change in the speed of the rotation of the earth  it has been concluded that the the moon moves away from the earth at the rate of about 13 cm per year. The present distance of the moon from the earth is 3,84,000 km. Thus, moon would have taken 2,953,846,000 years to move 3,84,000 km away from the earth. On this basis the age of the earth has been estimated as 4000 million (4 billion) years.