CBSE Class 6 Geography Ch 1: Earth in Solar System

Chapter 1: The Earth in the Solar System

Social Science - Geography (CBSE Class 6)

Chapter Summary

• On a clear night, we can see countless twinkling objects, some bright and some dim. These are celestial bodies.
• The Full Moon (Poornima) appears once in about a month. A fortnight later, you cannot see it at all. This is a New Moon night (Amavasya).
• The Sun, the Moon, and all those objects shining in the night sky are called celestial bodies.
• Some celestial bodies are very big and hot. They are made up of gases. They have their own heat and light, which they emit in large amounts. These celestial bodies are called stars. The Sun is a star.
• While watching the night sky, you may notice various patterns formed by different groups of stars. These are called constellations. Ursa Major or Big Bear is one such constellation. The Saptarishi (Sapta–seven, rishi–sages) is a group of seven stars that forms a part of the Ursa Major constellation.
• In ancient times, people used to determine directions during the night with the help of stars. The Pole Star indicates the north direction. It always remains in the same position in the sky.
• Some celestial bodies do not have their own heat and light. They are lit by the light of the stars. Such bodies are called planets. The word ‘planet’ comes from the Greek word “Planetai” which means ‘wanderers’.
• The Earth is a planet. It gets all its heat and light from the Sun.
• The Solar System consists of the Sun, eight planets, satellites, and some other celestial bodies known as asteroids and meteoroids.
• The Sun is at the centre of the solar system. It is huge and made up of extremely hot gases. It provides the pulling force that binds the solar system. It is the ultimate source of heat and light for the solar system. The Sun is about 150 million kilometres away from the Earth.
• There are eight planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. In order of their distance from the Sun. A common mnemonic to remember the order is: "My Very Efficient Mother Just Served Us Nuts."
• All the eight planets move around the Sun in fixed, elongated paths. These paths are called orbits.
• Mercury is the closest planet to the Sun. It takes only about 88 days to complete one round along its orbit.
• Venus is considered as ‘Earth’s twin’ because its size and shape are very much similar to that of the Earth.
• The Earth is the third nearest planet to the Sun. In size, it is the fifth largest planet. It is slightly flattened at the poles, hence its shape is described as a Geoid. Geoid means an Earth-like shape.
• Conditions favourable to support life are probably found only on the Earth. It is neither too hot nor too cold. It has water and air, which are essential for survival. Because of the presence of water, the Earth is called a ‘blue planet’.
• The Moon is the Earth’s only natural satellite. Its diameter is only one-quarter that of the Earth. It appears so big because it is closer to our planet than other celestial bodies (about 3,84,400 km away).
• The Moon moves around the Earth in about 27 days. It takes exactly the same time to complete one spin. As a result, only one side of the Moon is visible to us on the Earth.
• A satellite is a celestial body that moves around the planets in the same way as the planets move around the Sun.
• Besides the planets, there are thousands of tiny bodies which also move around the Sun. These bodies are called asteroids. They are found between the orbits of Mars and Jupiter. Scientists believe that asteroids are parts of a planet which exploded many years back.
• The small pieces of rocks which move around the Sun are called meteoroids. Sometimes these meteoroids come near the Earth and tend to drop upon it. During this process, due to friction with the air, they heat up and burn, causing a flash of light. Sometimes, a meteor without being completely burnt, falls on the Earth and creates a hollow.
• A galaxy is a huge system of billions of stars, and clouds of dust and gases. Our solar system is a part of the Milky Way galaxy (Akash Ganga). In ancient India, it was imagined to be a river of light flowing in the sky.
• There are millions of such galaxies that make up the Universe. It is difficult to imagine how big the universe is.

Questions and Answers

1. Answer the following questions briefly.

1. How does a planet differ from a star?

   Answer:

   • Stars: Are very big and hot celestial bodies, made up of gases. They have their own heat and light, which they emit in large amounts. The Sun is a star.
   • Planets: Are celestial bodies that do not have their own heat and light. They are lit by the light of stars. They revolve around a star in an orbit. The Earth is a planet.

2. What is meant by the ‘Solar System’?

   Answer: The Solar System refers to the Sun, eight planets, satellites, and some other celestial bodies like asteroids and meteoroids. All these bodies revolve around the Sun.

3. Name all the planets according to their distance from the Sun.

   Answer: The planets in order of their distance from the Sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

4. Why is the Earth called a ‘blue planet’?

   Answer: The Earth is called a ‘blue planet’ because, when viewed from outer space, it appears blue. This is due to the presence of water, which covers over two-thirds of its surface.

5. What is a galaxy?

   Answer: A galaxy is a huge system of billions of stars, and clouds of dust and gases. Our solar system is a part of the Milky Way galaxy. There are millions of such galaxies that make up the Universe.

2. Tick the correct answer.

1. The planet known as the ‘Earth’s Twin’ is

   (i) Jupiter (ii) Saturn (iii) Venus

2. Which is the third nearest planet to the Sun?

   (i) Venus (ii) Earth (iii) Mercury

3. All the planets move around the Sun in a

   (i) Circular path (ii) Rectangular path (iii) Elongated path

4. The Pole Star indicates the direction to the

   (i) South (ii) North (iii) East

5. Asteroids are found between the orbits of

   (i) Saturn and Jupiter (ii) Mars and Jupiter (iii) The Earth and Mars

3. Fill in the blanks.

1. A group of stars forming various patterns is called a constellation.

2. A huge system of stars is called a galaxy.

3. Moon is the closest celestial body to our Earth.

4. Earth is the third nearest planet to the Sun.

5. Planets do not have their own heat and light.