1. CHAPTER 2
EARTH OUR HOME

2. Learning Outcomes
You Will Learn:
that the Earth is fragile

3. Lead-in: Looking at the Earth from Space (Answers)
World’s first view of Earth (23 August 1966)
Taken by a spacecraft near the moon
(Source: NASA)
I would feel in awe of the view of the Earth from outer space and even find it mysterious.
Yes, the Earth could be destroyed if a large asteroid hits our planet. This is a theory that has often been used to explain the extinction of dinosaurs.

4. The Solar System

5. (Third planet from the Sun)
The Solar System
SUN
MERCURY
VENUS
EARTH
(Third planet from the Sun)
JUPITER
PLUTO
URANUS
MARS
SATURN
NEPTUNE
The solar system consists of nine planets and the Sun
The nine planets orbit round the Sun
The planet closest to the Sun takes the shortest time to orbit around the Sun
The Earth is the third planet from the Sun

6. Revolution of the Earth
The Earth, while rotating on its axis, also revolves around the Sun
One orbit or revolution of the Earth around the Sun takes 365 ¼ days (1 year)
Due to the revolution and tilting of the Earth, different places on Earth receive different amount of heat and sunlight from the Sun
The combined effect of the Earth's revolution and its tilt results in the seasons in some parts of the world
Earth tilted at 23.5o
Equator
Axis
Southern
Hemisphere
Northern
December
Winter in Northern Hemisphere
Summer in Southern Hemisphere
June
Summer in Northern Hemisphere
Winter in Southern Hemisphere

7. Rotation of the Earth The Earth spins from west to east on its axis
This movement is known as a rotation
The Earth’s axis of rotation points in the same direction throughout its revolution around the sun
One rotation takes 24 hours (1 day) to complete
Axis
The part of the Earth
that faces the Sun experiences day.
North Pole
The part of the Earth
that does not face the
Sun experiences night.
South Pole

8. Fragile Earth
To our knowledge, the Earth is the only planet in the Solar System with an environment that is suitable for living things
The Earth provides us with the materials and conditions to live comfortably
However the Earth is fragile because it can be damaged by human activities, such as pollution and depletion or Earth’s natural resources
Therefore we have to learn to use the Earth’s resources wisely to protect our environment

9. Skills Builder: Suggested Answers
For life to be possible on a planet, it must have:
gravity somewhere between 50% and 150% of the Earth's gravity;
an atmosphere with the right amount of oxygen, very little carbon dioxide, lots of liquid water; and
an average temperature somewhere above freezing point of water and somewhere below boiling point of water

10. Additional Resources from Multimedia TEACH Resources Photo Bank
Image A
Image B
Photo 2-1
As far as we know, the Earth is the only planet in the Solar System that supports life. Compare the satellite image of the Earth (Image A) with the satellite image of Mars (Image B). How are they different?

11. Additional Resources from Multimedia TEACH Resources Photo Bank
Polar ice cap in 1979
Polar ice cap in 2003
Photo 2-2
Human activities have an impact on the physical environment. The satellite images, taken in 1979 and 2003, show that the polar ice caps in the North Pole have reduced in size to a large extent over a 24-year period. Why do you think so?