The earth has two types of motions: rotation ( घूर्णन ) and revolution ( परिक्रमण ) . 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 (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 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 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 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. Revolution takes 365¼ days (one year) to revolve around the sun. We ge...