New Science eTextbook 4A (UPC)

2 Movement of the Earth Unit 1 About the Earth

1 Why is there day and night? 1. Day and night repeat on a regular basis. Why? Make a guess.

2. The Earth rotates on its axis, which is an imaginary line passing through the North Pole and the South Pole. Shine a torch on a globe to simulate how the Sun shines on the rotating Earth. Then, explain why there is day and night.

1

paper puppet

Hong Kong

Earth’s axis

Use some tape to fix the paper puppet at the location of Hong Kong on the globe. Shine the torch on that spot.

2

3

Without moving the torch, rotate the globe anticlockwise for a half turn.

Rotate the globe anticlockwise for another half turn.

Explanation: It is bright / dark in Hong Kong when it faces the Sun, so it is

day / night . When the globe rotates for a half turn, Hong Kong turns away from the Sun. It is bright / dark there, so it is day / night .

Quick Check

The cycle of day and night is caused by the

of the Earth.

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