NCERT Class 4 EVS Our Wondrous World Chapter 10 Our Sky PDF Download

Chapter 10: Our Sky

Have you ever looked up at the sky? It appears different at various times of the day. The colour of the sky changes in the morning, afternoon and at night. The Sun's colour also appears to change. Even, the size and the shape of the Moon seem to change over time. The activities of birds, animals, trees and humans also vary during the course of the day.

Pictures of the Sky

Draw

Draw a picture of the sky as it appears in the morning, afternoon and at night, in the spaces given below.

[Figure: Morning Sky, Afternoon Sky, and Night Sky drawing spaces, See in your textbook]

Write

Write down what you observe in the sky during the morning, afternoon and at night, in the table given below. A few boxes are filled for you. You may expand your table by adding new points.

• Share your observations with your classmates and compare them.
• Have you observed any change in the activities, and the behaviour of animals and plants at different times of a day? Discuss these changes with your friends and make a list.

Can you guess the brightest object in the sky? It is the Sun! In fact, it is so bright that the other stars cannot be seen when it is present in the sky. The Sun gives us light and heat.

In the sky, the Sun is the most visible object. The Sun appears to rise in the morning. Then, it seems to move up till it comes overhead. Slowly, it appears to move downwards on the other side of the sky till it disappears. We all enjoy this visible journey of the Sun in the sky.

Discuss

Have you observed the changes during sunrise and sunset?

When the Sun rises:

1. How does the sky look?
2. What do the birds and animals do?
3. What changes do we find at home?

When the Sun sets:

1. How does the sky look?
2. What do the birds and animals do?
3. What changes do we find at home?

Note to the Teacher

Encourage students to observe and share various changes in the activities, and the behaviour of plants and animals, including humans at different times of the day.

Teacher's Note

When you observe the sky at different times, notice how the Sun's position and colour change. In the morning, the Sun is low and often appears orange or red. By noon, it is high and bright yellow or white. In the evening, it is low again and appears orange or red. These changes happen because of where the Sun is in the sky, not because the Sun itself is changing colour.

The Shadows

Have you ever noticed your shadow moving along with you? If you run, the shadow seems to be running with you. If you make different poses, the shape of the shadow changes. Let us explore some interesting things about the shadows.

[Figure: Early morning shadow, Noon shadow, and Evening shadow of a person, See in your textbook]

In the pictures above, what are the differences in the shadows? Shadows at morning are long, noon shadows are short and shadows at evening are long again. However, the evening shadows appear in the opposite direction of morning shadows.

[Figure: A girl with thought bubbles asking: How does my shadow change? Does this happen to all the objects? Are shadows formed only in the sunlight? I wonder why these changes occur?, See in your textbook]

Find out

Let us try something interesting.

1. Take a torch and a stick. Close the doors and windows to make the room dark.
2. Hold the stick in one place and turn on the torch. Shine the torchlight on the stick.
3. Observe the changes in the shadow of the stick, in the following situations:
   1. Move the stick back and forth.
   2. Change the direction of the torch.

[Figure: A child holding a torch and shining it on a stick to observe shadows, See in your textbook]

Think and answer the following questions.

• If we change the distance of the source of light from the stick (an object), how will the shadow change?
• If we change the direction of the torch (source of light), how will the shadow change?

If the object is close to the source of light, the shadow is bigger. If the direction of the source of light changes, the direction of the shadow also changes. We observe that shadows in the morning and evening form in different directions. Why does this happen?

Teacher's Note

Shadows depend on two things: how far the light source is from the object, and which direction the light is coming from. When the light is close to an object, the shadow becomes larger. When the light comes from a different direction, the shadow points in a different direction. The Sun's position in the sky changes throughout the day, so morning shadows and evening shadows point in opposite directions.

Key Points

• The sky looks different at different times of the day. In the morning it often appears orange, during the day it is blue, and at night it is dark with stars and the Moon visible.
• The Sun appears to move across the sky from morning to evening, and its light and heat are most strong when it is highest in the sky at noon.
• Shadows form when light from a source like the Sun or a torch is blocked by an object. The size and direction of a shadow depend on how close the light source is to the object and which way the light is shining.
• Morning shadows and evening shadows point in opposite directions because the Sun is in different positions in the sky at these times of day.
• All objects that block light will cast a shadow, not just people - this happens whenever light is present, whether from the Sun or from a torch.

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