The Earth in the Solar System

On a clear night, the sky is full of twinkling stars and the Moon. The Sun, the Moon and all objects shining in the night sky are called celestial bodies. Stars, like the Sun, have their own heat and light. Groups of stars forming patterns are constellations, such as Ursa Major or Saptarishi, and the Pole Star stays in the same position and shows the north direction. In this chapter you will learn about the solar system: the Sun at its centre and the eight planets that move around it in elliptical orbits, along with satellites, asteroids and meteoroids. The Earth is the third planet from the Sun and the fifth largest. It is called the blue planet because about two-thirds of its surface is covered by water, and it is the only planet known to support life. Its shape is a geoid. The Moon, its only natural satellite, is about 3,84,400 km away and always shows us the same side. Our solar system is part of the Milky Way galaxy.

Detailed Worksheet: The Earth in the Solar System Section A - Definitions (10 marks) 1. What are celestial bodies? Give two examples. (2 marks) 2. What is a constellation? Name one constellation. (2 marks) 3. Distinguish between a star and a planet. (2 marks) 4. What are asteroids? Where are most of them found? (2 marks) 5. What is a galaxy? Name the galaxy to which our solar system belongs. (2 marks) Section B - Calculations and Applications (15 marks) 6. The Sun is about 15,00,00,000 km away from the Earth, and light travels about 3,00,000 km per second. (i) Find the time light takes to reach the Earth in seconds. (ii) Express it in minutes and seconds. (iii) Write the distance in the International system with commas. (3 marks) 7. The Moon is about 3,84,400 km from the Earth. (i) If a spacecraft travels at 40,000 km per hour, about how long will it take to reach the Moon? (ii) The Moon takes about 27 days to revolve around the Earth; how many revolutions does it make in about 1 year (taking 1 year as 365 days)? (iii) Why do we always see the same side of the Moon? (3 marks) 8. Arrange the eight planets in order of their distance from the Sun. Which planet is the largest and which is the smallest? (3 marks) 9. About two-thirds of the Earth's surface is covered with water. (i) What fraction is land? (ii) If the Earth's total surface area is about 510 million square km, find the approximate area covered by water. (iii) Why is the Earth called the blue planet? (3 marks) 10. Give the reason: (i) the Earth is the only planet known to support life (ii) the Moon has no life (iii) Pluto is no longer called a planet. (3 marks) Section C - Diagrams (10 marks) 11. Draw a labelled diagram of the solar system showing the Sun, the eight planets in order, and the asteroid belt between Mars and Jupiter. (4 marks) 12. Draw the pattern of the Saptarishi (Ursa Major) constellation and show how two of its stars point to the Pole Star. (3 marks) 13. Draw a diagram showing the Moon revolving around the Earth and the Earth revolving around the Sun. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. The Earth has conditions favourable for life. (i) Explain the importance of its distance from the Sun. (ii) Why is the presence of water and air important? (iii) Why would life be difficult on Venus and on Neptune? (iv) What can humans do to protect these conditions on Earth? (5 marks) 15. The Moon appears bright at night but has no light of its own. (i) How does the Moon shine? (ii) Why are there no sounds on the Moon? (iii) Name the first person to step on the Moon and the year. (iv) Name one Indian mission to the Moon. (5 marks) 16. In ancient times, travellers used stars to find their way at night. (i) Which star helps find the north direction? (ii) Why does it appear fixed in the sky? (iii) How can the Saptarishi help locate it? (iv) Why are stars not visible during the day? (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Draw all diagrams neatly in pencil and label every celestial body.