CHAPTER 2 EARTH OUR HOME

Learning Outcomes You Will Learn: that the Earth is fragile

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.

The Solar System

(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

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

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

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

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

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?

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?