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Samacheer Kalvi 6th Social Science Books English Medium The Universe and Solar System

Social Science : Geography : Term 1 Unit 1 : The Universe and Solar System

A. Fill in the blanks.

1. The Universe was formed after __________________ explosion.

Ans : Big Bang

2. __________________ is the unit used to measure the distance between two celestial bodies.

Ans : Light year

3. __________________ is the centre of the solar system.

Ans : Sun

4. The word planet means __________________ .

Ans : wanderer

5. __________________  planet has many natural satellites.

Ans : Jupiter

6. India’s first ever mission to the moon is __________________ .

Ans : Chandrayan – I

7. Earth is inclined by __________________  degrees.

Ans : 231/2

8. The Equator faces the Sun directly on __________________ and __________________ .

Ans : 23rd September

9. At the time of Perihelion, the Earth is __________________ to the Sun.

Ans : closest

10. The line which divides day and night on the Earth’s surface is __________________ .

Ans : Terminatorline

B. Choose the best answer.

1. The movement of the Earth on its axis is called

  1. Revolution
  2. Seasons
  3. Rotation
  4. Circulation

Ans : Rotation

2. The Tropic of Capricorn faces the Sun directly on

  1. March 21
  2. June 21
  3. September 23
  4. December 22

Ans : September 23

3. The galaxy in which our solar system is found is

  1. Andromeda
  2. Magellanic clouds
  3. Milky Way
  4. Starburst

Ans : Milky Way

4. The only celestial body where man has successfully landed

  1. Mars
  2. Moon
  3. Mercury
  4. Venus

Ans : Moon

5. Which of the following planets can float on water?

  1. Jupiter
  2. Saturn
  3. Uranus
  4. Neptune

Ans : Saturn

C. Circle the odd one out

1. Venus, Jupiter, Neptune, Saturn

Ans : Venus

2. Sirius, Andromeda, Milky way, Magellanic clouds

Ans : Sirius

3. Pluto, Eris, Ceres, Io

Ans : Io

4. Comet, Asteroids, Meteorites, Dwarf planets

Ans : Dwarf planets

5. Rover, Orbiter, Aeroplane, Space shuttle

Ans : Aeroplane

D. Match the following:

1. Hottest PlanetMars
2. Ringed PlanetNeptune
3. Red PlanetVenus
4. Somersaulting PlanetSaturn
5. Coldest PlanetUranus

Ans : 1 – C, 2 – D, 3 – A, 4 – E, 5 – B

E. i) Consider the following statements.

1. Venus rotates from east to west.

2. The Tropic of Cancer faces the Sun on June 21.

3. Mars has rings around it.

Choose the correct answer using the codes given below.

  1. 1 and 2
  2. 2 and 3
  3. 1, 2 and 3
  4. 2 only

Ans : 1 and 2

ii) Consider the following statements.

Statement I : Earth is called a watery planet.

Statement II : The rotation of the Earth causes seasons.

Which of the statement(s) is/are true?

  1. I is true; II is wrong
  2. I is wrong; II is true
  3. Both the statements are true
  4. Statements I and II are wrong.

Ans : I is true; II is wrong

F. Name the following:

1. Cluster of stars.


2. The nearest galaxy to the solar system.


3. The brightest planet.


4. The living sphere.


5. The year which has 366 days.

Leap year

G. Answer in a sentence or two.

1. Name the inner planets.

The inner planets are Mercury, Venus, Earth, and Mars.

2. Pluto is no longer a planet. Reason out.

In August 2006, The international Astronomical union (IAU) downgraded the status of Pluto to that of dwarf planet.

3. What is perihelion?

Perihelion is the Earth’s closest position to the sun.

4. How many times in a year would you find the Sun overhead if you lived on 20°N Latitude?

Two times; It would be on 21st March and 23rd September.

5. Which celestial body shares its orbit with others? Give an example.

  • The dwarf planets share these orbits with others.
  • The five dwarf planets of the solar system are Pluto, Ceres, Eris, Makemake and Haumea.

H. Give reasons:

1. Why is Uranus called as the somersaulting planet?

The axis of urban is tilted so much that it appears to orbit the sun on its sides like on rolling ball, so Uranus called the somer saulting planet.

2. The surface of the moon has many craters.

  • Moon has no atmosphere.
  • The surface of the moon is characterized by craters created by the impact of meteors.

3. The velocity of Earth’s rotation is zero at poles.

  • The earth is a sphere.
  •  If is widest at the equator, becoming increasingly narrow further towards to top and bottom.
  • The velocity of Earth’s rotation varies from 1670 km/hr at equator and to 845 km/hr at 60° N and S and zero at the poles.

I. Answer in detail:

1. Distinguish between inner and outer planets.

Inner or Terrestrial planets

  • Mercury, Venus, Earth, Mars.
  • They are comparatively smaller in size.
  • They are composed of rocks the surface of the inner planets has mountains, volcanoes and craters.

Outer planets or Jovian planets or Gaseous giant:

  • Jupiter, Saturn, Uranus, Neptune
  • They are huge in size
  • Most of them are made of gas
  • All of the outer planets have rings orbiting them.

2. What are the effects of rotation and revolution?

  • It is spinning movement of the Earth on its axis.
  • The time taken by the earth to complete one rotation is called a day.
  • The rotation of the earth causes day and night. As the earth is spherical in shape only one half of it is illuminated by the sun at a time.
  • The other half remains dark.
  • The illuminated portion of the earth experiences day, whereas the darkened part of the earth experiences night.

Effect of Revolution:

  • It is the movement of the earth around the sun on its elliptical path.
  • The Earth takes 365¼ days to complete one revolution.
  • It revolves around the sun at a speed of 30km per second.

3. Explain the characteristics of the various spheres of the Earth.

The Earth is the most suitable planet to support life. It has three major components that we call as the realms of the Earth- lithosphere, hydrosphere and atmosphere.


The word lithosphere is derived from the Greek word Lithos, which means rocky. The Lithosphere is the land on which we live.


The word Hydro means water in Greek. The hydrosphere consists of water bodies such as oceans, seas, rivers, lakes, ice caps on mountains and water vapour in the atmosphere.


The word Atmo means air in Greek. Atmosphere is the envelope of air that surrounds the Earth. Different types of gases make up the atmosphere. The major gases are Nitrogen (78%) and Oxygen (21%).


The narrow belt of interaction among the lithosphere, the hydrosphere and the atmosphere, where life exists is known as Biosphere. Bio means life in Greek. It consists of distinct zones.

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