ROTATION AND REVOLUTION OF EARTH

 Rotation and revolution of the earth...

As you know that the earth has two types of motions,

namely rotation and revolution. Rotation is the

movement of the earth on its axis. The movement of

the earth around the sun in a fixed path or orbit is

called Revolution.

The axis of the earth which is an imaginary line,

makes an angle of 66½° with its orbital plane. The

plane formed by the orbit is known as the orbital plane.

The earth receives light from the sun. Due to the

spherical shape of the earth, only half of it gets light

from the sun at a time.

The portion facing

the sun experiences day while the other half away from

the sun experiences night. The circle that divides the

day from night on the globe is called the circle of

illumination. This circle does not coincide with the

axis.The earth takes about

24 hours to complete one rotation around its axis.

The period of rotation is known as the earthday. This is

the daily motion of the earth. 

What would happen if the earth did not rotate? The

portion of the earth facing the sun would always

experience day, thus bringing continuous warmth to

the region. The other half would remain in darkness

and be freezing cold all the time. Life would not have

been possible in such extreme conditions.

The second motion of the earth around the sun in

its orbit is called revolution. It takes 365¼ days (one

year) to revolve around the sun. We consider a year as

consisting of 365 days only and ignore six hours for

the sake of convenience.Indian

astronomer Aryabhata

had stated that ‘the

earth is round and

rotates on its own axis’.

Six hours saved every year are added to make one

day (24 hours) over a span of four years. This surplus

day is added to the month of February. Thus every

fourth year, February is of 29 days instead of 28 days.

Such a year with 366 days is called a leap year.

it is clear that the earth is

going around the sun in an elliptical orbit.

A year is usually divided into summer, winter, spring

and autumn seasons. Seasons change due to the change

in the position of the earth around the sun.