The Earth in the Solar System: NCERT Exercise Solutions
Welcome to the complete NCERT exercise solutions for Class 6 Social Science Geography Chapter 1 — The Earth in the Solar System. This page covers every intext question, chapter-end exercise question, MCQs, and exam tips aligned with the latest CBSE syllabus. All answers are written in simple, student-friendly language so you can understand and remember the concepts easily.
How to Use This Page
1. Read the Key Concepts section first for a quick recap of important terms. 2. Attempt the Intext Questions on your own before reading the answers — this builds understanding. 3. Study the Chapter-End Exercise Answers for detailed, exam-ready responses. 4. Practice the MCQs to test your recall and spot weak areas. 5. Review the Common Mistakes section to avoid losing marks in the exam. 6. Use the Exam Checklist before your test to make sure you have revised everything.
Key Concepts (Quick Recap)
| Term | Definition |
|---|
| Solar System | The Sun together with the eight planets, satellites, asteroids, comets, and other celestial bodies that revolve around it |
| Sun | The star at the centre of the solar system; a huge ball of hot, glowing gases that provides heat and light |
| Planet | A celestial body that revolves around the Sun in a fixed orbit and does not have its own light |
| Satellite | A celestial body that revolves around a planet; the Moon is Earth's natural satellite |
| Star | A huge ball of glowing gases that produces its own heat and light |
| Constellation | A group of stars forming a recognisable pattern in the night sky, e.g. Ursa Major, Orion |
| Asteroid | A small rocky body orbiting the Sun, mostly found in the asteroid belt between Mars and Jupiter |
| Meteor | A small piece of rock or dust from space that burns up brightly when it enters Earth's atmosphere (also called a "shooting star") |
| Galaxy | A vast system of millions or billions of stars, dust, and gas bound together by gravity; the Milky Way is our galaxy |
| Orbit | The fixed, elliptical path along which a planet or satellite revolves around the Sun or a planet |
Intext Questions
Q1. Why are we not able to see stars during the day time?
Answer
During the day, the Sun's light is extremely bright and scatters throughout the atmosphere. This scattered sunlight makes the sky appear bright and blue, which overwhelms the faint light coming from distant stars. Stars are still present in the sky during the day, but their light is too weak to be seen against the bright glare of the Sun. At night, without the Sun's scattered light, the sky becomes dark and we can easily see the stars.
Q2. What does the full moon look like?
Answer
The full moon appears as a complete, bright, circular disc in the night sky. During the full moon phase, the entire illuminated side of the Moon faces the Earth, so we see the whole Moon lit up. The full moon is the brightest object in the night sky after Venus and provides enough light to see objects outdoors on clear nights.
Q3. Why is the Earth called a unique planet?
Answer
The Earth is called a unique planet because it is the only known planet that supports life. Several conditions make this possible: (a) Earth has water in liquid form — about 71% of its surface is covered by water, which is essential for all living organisms. (b) Earth has a breathable atmosphere with the right mix of oxygen, nitrogen, and other gases. (c) The distance of Earth from the Sun gives it just the right temperature — neither too hot nor too cold — making it suitable for life. (d) Earth has a protective blanket of atmosphere that shields it from harmful solar radiation. No other planet in the solar system has all these conditions together.
Q4. How are constellations identified? Name any two constellations.
Answer
Constellations are identified by the patterns or shapes formed by groups of stars in the night sky. Ancient observers imagined these patterns as figures of animals, objects, or mythological characters and gave them names. The stars in a constellation appear close together from Earth, though they may be very far apart in space. Two well-known constellations are:
- Ursa Major (also called the Great Bear or Saptarishi in Hindi) — it has seven prominent stars arranged in a pattern resembling a bear.
- Orion (also called the Hunter) — it has a distinctive belt of three stars in a row and is visible in the winter sky.
Q5. What is the difference between a star and a planet?
Answer
A star and a planet differ in several important ways:
- A star has its own light and heat. It is made up of hot, glowing gases. The Sun is an example of a star.
- A planet does not have its own light. It shines by reflecting the light of the star it revolves around. Planets are solid or gaseous bodies that revolve around a star in a fixed orbit.
- Stars are much larger and hotter than planets. Stars twinkle in the night sky, while planets generally shine with a steady light.
Chapter-End Exercise Questions
Q1. Answer the following questions briefly.
Answer
(a) Why is the Earth called a unique planet?
The Earth is called a unique planet because it is the only planet in the solar system known to support life. This is possible because of three special conditions: (i) Earth has plenty of water in liquid form — about 71% of its surface is covered by oceans, seas, rivers, and lakes. (ii) Earth has an atmosphere rich in oxygen and nitrogen, which is essential for breathing and for protecting life from harmful radiation. (iii) The temperature on Earth is moderate because it is at just the right distance from the Sun — not too hot like Mercury or Venus, and not too cold like the outer planets. These conditions are not found on any other planet, which makes Earth truly unique.
(b) What is the solar system?
The solar system is a family of celestial bodies that includes the Sun at its centre and all the objects that revolve around it. These objects include eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune), their moons (satellites), dwarf planets like Pluto, asteroids, comets, and meteors. The Sun's immense gravitational pull keeps all these bodies in their orbits. The solar system formed about 4.6 billion years ago from a giant cloud of gas and dust.
(c) Name all the planets in order from the Sun.
The eight planets in order of their distance from the Sun are: 1. Mercury — closest to the Sun, smallest planet 2. Venus — second from the Sun, hottest planet 3. Earth — third from the Sun, the only planet with life 4. Mars — fourth from the Sun, called the Red Planet 5. Jupiter — fifth from the Sun, largest planet 6. Saturn — sixth from the Sun, known for its beautiful rings 7. Uranus — seventh from the Sun, rotates on its side 8. Neptune — eighth and farthest from the Sun
A useful mnemonic to remember the order: My Very Educated Mother Just Served Us Noodles.
(d) Why is the Earth called the Blue Planet?
The Earth is called the Blue Planet because when viewed from space, it appears mostly blue. This is because about 71% of Earth's surface is covered by water in the form of oceans, seas, rivers, and lakes. The vast expanse of water reflects the blue colour of the sky and gives Earth its distinctive blue appearance. No other planet has such a large amount of water on its surface.
(e) What are constellations? Name one constellation.
Constellations are groups of stars that form recognisable patterns or shapes in the night sky. People in ancient times named these patterns after animals, objects, or mythological figures they resembled. Constellations help navigators and astronomers locate stars and find directions. One well-known constellation is Ursa Major (the Great Bear), which contains the group of seven stars called the Big Dipper or Saptarishi.
Q2. What is the difference between a star and a planet?
Answer
| Feature | Star | Planet |
|---|
| Own light | Has its own light and heat | Does not have its own light; reflects light from a star |
| Composition | Made of hot, glowing gases | Made of solid, liquid, or gaseous material |
| Size | Much larger than planets | Much smaller than stars |
| Motion | Appears stationary from Earth (relative position changes very slowly) | Revolves around a star in a fixed orbit |
| Twinkling | Twinkles in the night sky | Shines with a steady light |
| Example | The Sun, Sirius, Pole Star | Earth, Jupiter, Mars |
Q3. Why do we see only one side of the Moon?
Answer
We always see only one side of the Moon from the Earth because the Moon takes approximately the same amount of time to rotate on its axis as it takes to revolve around the Earth — about 27.3 days. This is called synchronous rotation or tidal locking. Because the rotation period equals the revolution period, the same hemisphere of the Moon always faces the Earth. The other side of the Moon, which we never see from Earth, is called the far side or the dark side of the Moon (though it does receive sunlight).
Q4. Fill in the blanks.
Answer
(a) The Sun is a \_\_\_\_\_\_\_\_\_ star. Answer: The Sun is a star.
(b) The planet known as the Red Planet is \_\_\_\_\_\_\_\_\_. Answer: The planet known as the Red Planet is Mars.
(c) A group of stars forming a recognisable pattern is called a \_\_\_\_\_\_\_\_\_. Answer: A group of stars forming a recognisable pattern is called a constellation.
(d) The Earth is the \_\_\_\_\_\_\_\_\_ planet from the Sun. Answer: The Earth is the third planet from the Sun.
(e) The largest planet in the solar system is \_\_\_\_\_\_\_\_\_. Answer: The largest planet in the solar system is Jupiter.
Q5. State whether the following statements are True or False.
(a) The Sun is the closest star to the Earth. Answer:
AnswerTrue The Sun is the closest star to the Earth, at an average distance of about 150 million kilometres.
(b) Pluto is a planet. Answer:
AnswerFalse In 2006, the International Astronomical Union (IAU) reclassified Pluto as a dwarf planet, so it is no longer considered one of the eight major planets.
(c) All planets have natural satellites. Answer:
AnswerFalse Not all planets have natural satellites (moons). Mercury and Venus do not have any moons.
(d) The Moon is a satellite of the Earth. Answer:
AnswerTrue The Moon is Earth's only natural satellite.
(e) Jupiter has the maximum number of moons. Answer:
AnswerTrue Jupiter has the largest number of confirmed natural satellites (moons) among the planets in the solar system.
Q6. Match the following.
Answer
| Column I | Column II |
|---|
| (i) Planet farthest from the Sun | (c) Neptune |
| (ii) Planet nearest to the Sun | (d) Mercury |
| (iii) Planet known as the Red Planet | (e) Mars |
| (iv) Planet known as the Blue Planet | (a) Earth |
| (v) Largest planet in the solar system | (b) Jupiter |
MCQ Practice
Choose the correct option for each question.
1. Which is the closest planet to the Sun?
Answer
- (a) Venus
- (b) Mercury ✓
- (c) Earth
- (d) Mars
2. Which planet is known as the Blue Planet?
Answer
- (a) Mars
- (b) Venus
- (c) Earth ✓
- (d) Neptune
3. Which of the following is a constellation?
Answer
- (a) The Sun
- (b) Ursa Major ✓
- (c) The Moon
- (d) Jupiter
4. How many planets are there in the solar system?
Answer
- (a) Seven
- (b) Eight ✓
- (c) Nine
- (d) Six
5. The planet that has beautiful rings around it is:
Answer
- (a) Jupiter
- (b) Mars
- (c) Saturn ✓
- (d) Venus
6. Which planet is called the Red Planet?
Answer
- (a) Venus
- (b) Jupiter
- (c) Saturn
- (d) Mars ✓
7. A shooting star is actually:
Answer
- (a) A star that has fallen
- (b) A meteor burning up in the atmosphere ✓
- (c) A comet
- (d) A satellite
8. The Pole Star indicates the direction of:
Answer
- (a) South
- (b) East
- (c) North ✓
- (d) West
9. Which planet has the largest number of natural satellites (moons)?
Answer
- (a) Saturn
- (b) Jupiter ✓
- (c) Uranus
- (d) Neptune
10. The Earth appears blue from space because:
Answer
- (a) The sky is blue
- (b) Most of the Earth's surface is covered with water ✓
- (c) The atmosphere is blue
- (d) The land is blue
Common Mistakes to Avoid
1. Confusing "star" with "planet": Stars have their own light (like the Sun); planets do not. Many students write that planets "shine" — remember, planets only reflect the light of their star.
2. Counting Pluto as a planet: Since 2006, Pluto is classified as a dwarf planet. The solar system has eight planets, not nine. Writing "nine planets" will cost you marks.
3. Writing "constellation" as a single star: A constellation is a group of stars forming a pattern, not a single star. Never write "a constellation is a bright star."
4. Confusing asteroid and meteor: An asteroid is a small rocky body that orbits the Sun (found mainly between Mars and Jupiter). A meteor is a piece of rock or dust that enters Earth's atmosphere and burns up, producing a streak of light (shooting star). They are not the same thing.
5. Saying "the Moon has no light at all": The Moon does not produce its own light, but it reflects sunlight. Saying "the Moon has no light" is incomplete — say "the Moon has no light of its own; it reflects sunlight."
6. Mixing up "rotation" and "revolution": Rotation is spinning on an axis (Earth rotates in 24 hours, giving us day and night). Revolution is orbiting around the Sun (Earth revolves in 365.25 days, giving us a year). Do not use them interchangeably.
Exam Checklist
Before your exam, make sure you can tick off every item below:
- [ ] I can define the solar system and name all its components (Sun, planets, satellites, asteroids, comets, meteors).
- [ ] I can list all eight planets in the correct order from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
- [ ] I can explain why Earth is called a unique planet (water, atmosphere, suitable temperature, life).
- [ ] I can explain why Earth is called the Blue Planet (71% water surface).
- [ ] I can state the difference between a star and a planet (own light vs reflected light, size, twinkling).
- [ ] I can define a constellation and name at least two (Ursa Major, Orion).
- [ ] I can explain why we see only one side of the Moon (synchronous rotation).
- [ ] I can distinguish between asteroid, meteor, and comet.
- [ ] I can define orbit, galaxy, and satellite with examples.
- [ ] I know that Pluto is a dwarf planet (not one of the eight major planets) and can explain why.
Quick Reference: Planets at a Glance
| Planet | Distance from Sun (approx.) | Special Feature |
|---|
| Mercury | 58 million km | Smallest planet, no atmosphere |
| Venus | 108 million km | Hottest planet, rotates in opposite direction |
| Earth | 150 million km | Only planet with life, 71% water |
| Mars | 228 million km | Red Planet, has the tallest volcano (Olympus Mons) |
| Jupiter | 778 million km | Largest planet, Great Red Spot |
| Saturn | 1,427 million km | Beautiful ring system made of ice and rock |
| Uranus | 2,871 million km | Rotates on its side, appears blue-green |
| Neptune | 4,497 million km | Farthest planet, has the strongest winds |
Key Takeaways
- The solar system consists of the Sun and everything that orbits it — planets, satellites, asteroids, comets, and meteors.
- The Sun is the ultimate source of heat and light for the entire solar system.
- Earth is unique because it has water, a life-supporting atmosphere, and a moderate temperature.
- Stars produce their own light; planets reflect light from their star.
- Constellations are patterns formed by groups of stars and have been used for navigation since ancient times.
- The Moon shows only one face to Earth because its rotation and revolution periods are equal.
- Remember: the solar system has eight planets (Pluto is a dwarf planet).
Study these solutions thoroughly, practise the MCQs, and revise using the checklist above. Good luck with your exam!
