NCERT Book Class 6 Social Science (Geography) Chapter 3 Motions of the Earth

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MOTIONS OF THE EARTH

Let’s Do As you know that the earth has two types of motions,
namely rotation and revolution. Rotation is the
Take a ball to
movement of the earth on its axis. The movement of
represent the
earth and a
the earth around the sun in a fixed path or orbit is
lighted candle to represent called Revolution.
the sun. Mark a point on The axis of the earth which is an imaginary line,
the ball to represent a makes an angle of 66½° with its orbital plane. The
town X. Place the ball in plane formed by the orbit is known as the orbital plane.
such a way that the town The earth receives light from the sun. Due to the
X is in darkness. Now spherical shape of the earth, only half of it gets light
rotate the ball from left to from the sun at a time (Figure 3.2). The portion facing
right. As you move the ball the sun experiences day while the other half away from
slightly, the town will the sun experiences night. The circle that divides the
have its sunrise. As the day from night on the globe is called the circle of
ball continues to move, illumination. This circle does not coincide with the
the point X gradually gets
axis as you see in the Figure 3.2. The earth takes about
away from the sun. This
is sunset. 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.

Figure 3.1 : Inclination of the Earth’s
axis and the orbital plane Figure 3.2 : Day and Night on the Earth due to rotation