# Shape and Spin of Earth

#### Students’ Learning Outcomes

·         Describe the shape of Earth.
·         Relate the Earth’s spin with the appearance of day and night.

#### Information for Teachers

·         The Earth is not flat. Instead it is round in shape.
·         It is a big sphere like a football.
·         The Earth spins about its own axis like a top. The axis of earth is an imaginary line that passes through north and south poles of the earth.
·         The days and night are caused by the spin of the Earth.
·         The side of the Earth that faces the sun has day and the side that is away from the sun has night.
·         The Earth completes one spin rotation in 24 hours.

#### Material / Resources

Torch, piece of chalk, globe, football, textbook

#### Worm up activity

·         Ask the students some questions like:
v  What do you think is the shape of the Earth?
v  How do you know this?
·         Show them a football and ask: if a small insect lived on this ball, what would it think the shape of the ball is?
(Expected response: The surface of small part of the ball will look like a flat surface)
·         Inform the students that the proof of the Earth’s being a sphere is provided by a ship approaching the sea shore. When the ship is far away, only the mast (a tall flag pole) of the ship is initially seen. The lower part of the ship appears later when the ship gets closer to the shore. If the Earth were flat, all parts of the ship would appear at the same time.
·         The picture of the earth taken from space also shows that the earth is a sphere.

#### Activity 1

·         Take a top and ask 2 or 3 students to spin it on the table or floor turn by turn.
·         Ask the students: What is a spin motion?
(Expected response: When an object rotates about its axis it is called as spin motion)
·         After explaining the spin motion of the top, ask them: How does the earth spin?
(Expected response: The earth spins about its axis like a top or globe)
(Expected response: about the nail fixed at the center on its lower side)
·         Inform them that this nail is the axis of the top. The axis of the Earth is an imaginary line that passes through the north and south poles of the Earth.

#### Activity 2

·         Show a globe to the students. Call a student and ask him to start from a point on the globe and trace the path along the surface of the globe to reach the starting point again.
·         Ask the students: imagine the Earth like a globe; can we make a round trip around it?
·          Ask the students to consider the Earth as a sphere like globe. Then ask them: Would it be possible to reach the starting point if we go on moving towards any one direction?
(Expected response: Yes)
·         Ask them would it be possible to make a round trip if the Earth were flat?
(Expected response: No)
·         It means that the Earth is not flat. It is like a sphere in shape.

#### Activity 3

·         Place a world globe on the table in a dark room.
·         Ask the students to note that the axis of globe is slightly tilted.
·         Throw light on the globe by a torch.
·         Ask them: Has the whole surface of the globe been brightened or only one half of the globe facing the torch is brightened?
(Expected response: The surface facing the torch is brightened)
·         Ask them: is the other half in the dark?
·         Now rotate the globe slowly keeping the torch ON all the time.
·         Ask them: Whether the part of globe that faces the light brightens while the other portion remains in dark?
·         Inform them that the Sun also brightens the Earth is lit by the Sun while the other half is always in dark. There is day in the bright part of the Earth and night in the dark part. Day and night are caused by the spin of the Earth like this globe.

#### Sum up / Conclusion

·         The Earth is not flat but it is like a sphere.
·         The Earth spins about its own axis.
·         The day and night appear due to spin of the Earth about its axis.

#### Assessment

·         Show them the following picture or draw it on the board.
·         Ask the students to observe the picture carefully and answer the following questions:
v  Which places are in day light in this picture?
v  Which place is entering from night into day?
v  The Earth spins on its axis. What do we call the ends of this axis?   (poles)