WBBSE Solutions For Class 9 Geography And Environment Chapter 1 Earth As A Planet

WBBSE Chapter 1 Earth As A Planet Long Answers Questions

Question 1. The Earth is not flat, it is almost spherical—Discuss with evidence.
Answer:  Evidence that the Earth is flat:

Though in ancient times the Earth was believed to be a flat plane or a disc, it is almost spherical—an oblate spheroid to be precise. A practical demonstration of the Earth’s spherical shape was proved by Magellan’s circumnavigation of the Earth (1519-1522). Recent photographs taken from outer space have also shown that the Earth is spherical. Some other points in support of this view are—

1. The study of other planets: When other planets of our solar system have been studied through powerful telescopes, they all have been observed to be spherical. Since the Earth is also a part of the solar system, it stands to reason that it would be spherical like the other planets.

Read and Learn Also WBBSE Solutions for Class 9 Geography And Environment

2. The study of the Earth’s shadow: When one studies the shadow of the Earth that falls on the Moon during a lunar eclipse, it is ‘seen to be circular. If an object casts a circular shadow, the Moon stands to reason that the object itself is also circular.

 

3. Observing a ship sailing out to sea: If we observe a ship that has just set sail from the shore, we will see that the ship is not visible after some time even with the help of binoculars or telescopes. This happens because of the curvature of the Earth’s surface. If the Earth had been a flat plane, the ship would never have disappeared from our line of sight.

4. Observing the horizon: The boundary where the sky seems to meet the ground or the sea is known as the horizon. The visible horizon marks the end of our line of sight. As we go higher up in an aeroplane or up a mountain, the visible horizon becomes more distant and its circumference seems to increase. As a result of which the line of horizon appears circular. If the Earth had been a flat plane, the circumference of the horizon line would not have increased with the increase in altitude of the observer’s position; instead, it would have remained the same.

5. Bedford Level Experiment: In 1870, renowned naturalist and surveyor Alfred Russel Wallace (A.R. Wallace) put in 3 sticks of equal height and diameter in a straight line at the 1-kilometre intervals in the Bedford Canal in the United Kingdom.

Through a telescope, he observed that the second stick seemed higher than the first and third sticks. This proved that the Earth is round. If the  Earth would have been flat, the tops would have been in a straight line

6. Sunrise and sunset: The Earth’s spherical shape causes countries in the Eastern Hemisphere to experience sunrise and sunset earlier than those in the Western Hemisphere. If the Earth had been flat, then sunrise and sunset would have occurred simultaneously at all places on the Earth.

Question 2. Why is the Earth called an oblate spheroid? Give a reason for your answer.
Answer: Reasons for the Earth being an oblate spheroid:

A sphere with a bulged-out centre and flattened Poles is defined as an oblate spheroid. The equatorial region of the. Earth is bulged out and the polar regions are flattened due to the Earth’s rotation, which is why the Earth is considered an oblate spheroid. There is some evidence which proves that the Earth is an oblate spheroid. They are

1. Polar diameter is less than equatorial diameter: The equatorial diameter: The Earth is 12,757km whereas the polar diameter is 12,714km. If the Earth had been a perfect sphere, then the 1 diameter would have been the same.

2. Difference in the time given by the same pendulum clock: In 1671 the French astronomer, Jean Richer, observed that his pendulum clock was running 214 minutes slower when he was in Cayenne (5°N), the capital of French Guiana, in South America.

However, the same pendulum clock would show the correct time in Paris (49°N). This is because the period of oscillation of the pendulum depends on the gravitational pull of a particular place, which is different in different locations. Sir Isaac Newton used this example later to show that places nearer to the equatorial radius are greater than its polar radius—or that the Earth is oblate-spheroid in shape.

3. Rotational movement of the Earth: When a spherical object rotates continuously, a centrifugal force acts on it. Therefore, the middle part bulges at Mariana Trench in the Pacific Ocean. At the same time, the polar areas flatten. The Earth has been continuously rotating on its axis since its origin. This is why the Earth has become an oblate spheroid in shape.

4. Variation in weight: The regions closer to the Earth’s centre experience greater gravitational pull than those farther away. Since the Earth is an oblate spheroid, the Poles are closer to the Earth’s centre and thus experience greater gravitational force. As a result, all objects weigh more at the Poles than at the Equator.

5. Variation in curvature: Oblate spheroids vary from north to south. It is observed that the smaller the circle, the greater the curvature. In the case of the Earth, the curvature is observed to be lesser at the Equator than at the Poles. This means the Earth is bulged out at the centre and flattened at the Poles. Therefore, from the variation in curvature, we can deduce that the Earth is an oblate spheroid.

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WBBSE Class 9 Geography Chapter 1 Earth As A Planet Solutions

Question 3. ‘The shape of the Earth is like the Earth KmBt itself.’—Explain.
Answer:

The shape of the Earth is Like the Earth itself: When a spherical object rotates continuously a centrifugal force acts on it. Therefore, the middle part bulges out and at the same time, the polar areas flatten. The oblate spheroid shape has formed as the Earth continuously rotates on its axis from its origin. However further studies revealed that the shape of the Earth is not a perfect oblate spheroid either. This is because of some specific reasons.

Various landforms such as mountains, hills, plateaus, valleys and rifts are present on the Earth’s surface. Apart from these, waterbodies with their waves and high and low tides also exist. The highest point on the Earth’s surface is Mount Everest (8,848m) and the lowest point is Challenger Deep (10,994m) at Mariana Trench in the Pacific Ocean. Both waterbodies and continents exist around the equatorial region at different places. Therefore, all these prove the surface of the Earth is undulating and uneven.

Question 4. Discuss the main planets of our solar system.
Answer:

The main planets of our solar system:

The solar system is the name given to the Sun and the various planets, satellites, comets, asteroids and other heavenly bodies that move in their unique orbits around the Sun in space. The planet’s names and characteristics are listed in the table below.

 

Question 5. Describe the Earth as a planet.
Answer: Earth as a planet: The Earth is important in the solar system. The features of the Earth as a planet are as follows-

1. Location: The Earth is the third planet based on its distance from the Sun, after Mercury and Venus.
2. Distance from the Sun: The Earth’s average distance from the Sun is 149.6 million kilometres.
3. Shape: The shape of the Earth is like an oblate spheroid. The North and South Poles are flattened and the equatorial region bulges out a little.
4. Mass and area: The mass of the Earth is about 5.97219 x 1024 kg and its surface area is about 510,072,000 square km.
5. Diameter: The Earth’s equatorial diameter is 12,757 km and the polar diameter is 12,714 km (approx.)
6. Speed: The Earth revolves around the Sun while rotating on its axis. It takes 23 hours 56 minutes and 4 seconds to complete one rotation on its axis and 365 days 5 hours 48 minutes and 46 seconds to complete one revolution around the Sun.
7. Orbit: The Earth’s orbit is elliptical. The length of the orbit is about 960 million km.
8. Satellite: The Earth has only one satellite- the Moon. The Moon is at a distance of about 3,84,400 km from the Earth. It has no
   light of its own and is illuminated by the light of the Sun.
9. Structure: The exterior of the Earth is made up of hard rocks and its interior is made up of hot, viscous magma. About 71% of the Earth’s surface is water and 29% is land. The Earth’s atmosphere is primarily made up of nitrogen and oxygen.
10. Sustenance of life: The Earth is the only planet in the solar system that sustains life as we know it.

Question 6. Give a brief note on GPS. How does the shape of the Earth?
Answer:

GPS: The Global Positioning System (GPS) is a radio-based navigation system that can locate the exact position of someone or something on Earth, at any time. A further elaboration of the system is:

Location: Several artificial satellites have been launched into space to orbit the Earth at an altitude of about 20,200 km—the minimum of four artificial satellites.

2. Components: GPS consists of three major parts. They are

1. The space segment,
2. The control segment,
3. And the user segment.

3. Information: GPS is mainly capable of providing four types of information about a place. They are-

1. ‘X’ Latitude,
2. ‘Y’ = Longitude,
3. ‘Z’ = Altitude and @ ‘T’ = Time.

4. Usage: Though GPS was first developed in the USA in the 1970s by the U.S. Department of Defence for military purposes, the use of GPS every day became common in the 1990s. This system helps us to

1. Find out the exact location of a place on the Earth’s surface,
2. Find out the average elevation of a place,
3. Determine the direction of flying aircraft and sailing ships and
4. Make maps for various development projects.

Earth As A Planet Notes And Solutions For WBBSE Class 9

Application of GPS in understanding the shape of the Earth:

As the receives the signals sent from the artificial satellites positioned in space, the exact position on Earth can be determined. The GPS signals are so accurate and powerful that even a small variation in height can be easily determined. The following example will further explain this.

For instance, say three points (A, B and C) are marked at a distance of 10m from each other on the same latitude. The GPS information from all these places is noted: ‘ X’ = Latitude, Y’ = Longitude, ‘Z’ = Altitude and ‘T’ = Time.

A graphical representation of the entire data will give us a clear picture of the variation in the height of the points studied.

Question 4. Write a note on the uses of GPS.
Answer: The uses of GPS: The Global Positioning System (GPS) is a radio-based navigation system that can locate the exact position of an object on Earth, anytime and anywhere. The applications of GPS are as follows-

1. Town planning: GPS is used for town planning in most urban areas.
2. Shape of the Earth’s surface: GPS is used to determine the shape of the Earth’s surface.
3. Distance and ruggedness: GPS is used to determine the difference in distances and ruggedness between two places on the surface of the Earth.
4. Transportation system: GPS is useful for determining how to fly aircraft and sail ships or even for deciding road routes to different places.
5. Defence: Currently, defence forces use GPS to track movement and carry out rescue operations. GPS helps track any aircraft or ship that has met with an accident or gone missing.
6. Geometric location: The geometric location of any object on the surface of the Earth can be traced with the help of GPS.
7. Weather: Weather information can be found through GPS and dependable forecasts can be made on the same basis.
8. Cartography: Cartography becomes easier, more informative and more accurate if drawn on a computer using data gathered from GPS.

Question:5 ‘Earth is the abode of man.’ Explain. Or, Describe why life has been found only on Earth instead of all the other planets in the solar system.
Answer: Reasons why life has been found only on Earth instead of all the other planets in

The solar system:  Among all the planets in the solar system, the Earth is the only planet where life exists. This is because of suitable living conditions on Earth. So, Earth has become the home for humans and other living organisms.
The reasons for this are as follows.

Suitable temperature: The Earth receives light and heat from the Sun. Some of it is retained and the rest is reflected by the atmosphere. This helps regulate the Earth’s temperature and maintain it at an average of 15°C, which is suitable for life. The planets nearer to the Sun (such as Mercury and Venus) and farther away from the Sun (such as Jupiter and Saturn) cannot sustain life because they are either too hot or too cold.

Abundant availability of water: Life is not possible without water. Water constitutes 71% of the Earth’s surface. This is another major reason for the existence of life on Earth. No traces of water have been found on other planets like Jupiter or Venus.

Availability of oxygen: Oxygen in the Earth’s atmosphere is about 21%. Oxygen is needed to survive because it helps to breathe. Earth is the only planet where the oxygen content in the atmosphere is about 21%, which is helpful for the sustenance and growth of life.

Availability of food: The Earth’s environment is favourable for growing food. All the necessary elements such as soil, sunlight, water, gaseous elements (0 and N), and mineral components (Fe, Cu) are found in suitable proportions on Earth. The green plants eat from these elements and the food chain continues.

Abundance of sunlight: Sun is the source of all known energy, and life is impossible without sunlight. The first link of any food chain- the autotrophs- uses solar energy to produce food.

6. Other factors: Life has become possible on Earth also because of the following reasons-

1. The right proportion of gases in the atmosphere,
2. Weather elements such as the formation of clouds, rain,
3. Wind flow and others, the occurrence of day and night,
4. Occurrence of seasons and various other factors.

WBBSE Chapter 1 Earth As A Planet Short Answer Questions

Question 1. Why does the curvature of the circumference of the Earth gradually increase from the Equator to the Poles?
Answer:

The Curvature Of The Circumference Of The Earth Gradually Increase From The Equator To The Poles:-

1 In 1737, the Royal Academy of Science of France did a test to calculate the correct size, shape, circumference, etc. of the Earth. Hence, the academy accurately measured a certain curvature of the circumferences of the Earth’s three cities Quito (0°), Paris (49°N) and Lapland (68°N). It was seen that the length of curvature in Quito city is the lowest.

Medium in Paris and highest in Lapland. That means the length of the curvature of the circumference of the Earth gradually increases from the Equator to the Poles. This proves that the equatorial area of the Earth is bulged out and the Poles are flattened. For this, the length of the curvature is less in the equatorial region and greater in the Poles.

2. Recent data from artificial satellites show that—

1. The South Pole of the Earth is more flattened than the North Pole.
2. The North Pole is about 20m higher and the South Pole is 20m lower than a perfect oblate spheroid shape. If it would have been a perfect oblate spheroid, both would have been at the same height.
3. The latitudinal circumference is 8m more in the southern hemisphere than in the northern hemisphere.
4. Therefore, the shape of the Earth cannot be compared to the shape of any other object on the Earth. So, it can be said that the shape of the
5. Earth is like the Earth itself or the shape of the Earth is ‘geoid’.

Question 2. What roles have gravitational and centrifugal forces played in shaping the Earth as we know it today?
Answer: Roles Of Gravitational And Centrifugal Forces Played In Shaping The Earth:-

Gravitational and centrifugal forces have a prominent effect on the shape of the Earth. Since the distance of the equatorial region is the farthest from the centre of the Earth, the effect of gravity around the equatorial region is the least. Thus, the objects tend to move outwards and away from the centre of gravity causing the central part to bulge out.

On the other hand, the distance from the centre of the Earth and the effect of rotational force at the Poles is the least. Thus, the effect of gravity becomes maximum, and objects are pulled towards the centre of the Earth. As a result, the Poles have gotten flattened. Thus, the effect of two opposite forces has resulted in the geoid shape of the Earth.

Question 3. How can a pendulum clock be used to confirm the oblate spheroid shape of the Earth?
Answer: Pendulum Clock Is Used To Confirm The Oblate Spheroid Shape Of The Earth:-

In 1671, the French astronomer Jean Richer observed the speed of the pendulum in a few places on the Earth. He noticed that his pendulum clock was running 234 minutes slower when he was on Cayenne Island (5° N), in South America, the capital of French Guiana. However, the same pendulum clock would show the correct time when he was in Paris (49° N) the capital of France in Europe.

This is because the period of oscillation of the pendulum changes due to the difference in the gravitational pull that occurs with a change in latitude. If the period of oscillation of the pendulum clock at Cayenne is greater than at Paris, it implies that the gravitational force of the Earth is lower at Cayenne, indicating that Cayenne is at a greater distance from the centre of the Earth than Paris. This confirms that the Earth’s equatorial radius is greater than its polar radius or that the Earth’s shape is that of an oblate spheroid.

Question 4. How will you prove that the Earth is not an ideal oblate spheroid?
Answer: The Earth Is Not An Ideal Oblate Spheroid:-

The Earth is a sphere that has a bulged-out centre and flattened Poles. That’s why the Earth is a known example of an oblate spheroid. Its east-west (along the Equator) extension is a little more and the circumference of the north-south is relatively less. But, the Earth is not an ideal oblate spheroid, because-

1. Satellite images have revealed that the North Pole of the Earth is 20 metres high and the South Pole is 20 metres flat. Again, the middle of the northern hemisphere is 8 metres flat and the middle of the southern hemisphere is 8 metres bulged.
2. The surface of the Earth is not flattened everywhere. There are high points on the Earth’s surface like Everest (8848 m) and even lowest points like Mariana Trench (10916 m) in the Pacific Ocean.

Question 5. The Pole Star’s angle of elevation helps to determine that the Earth is spherical/—Explain.
Answer: The Pole Star’s Angle Of Elevation Helps To Determine That The Earth Is Spherical In Shape:-

The angle of elevation of the Pole Star helps to know that the Earth is round. The Pole Star is visible at different angles of elevation from different places on the Earth’s surface in the northern hemisphere. At the Equator, it is visible at 0°, from the Tropic of Cancer at 2334°, and from the North Pole at 90° This happens only because the Earth is spherical. Had the Earth been just a plane, the Pole Star would have been visible at the same angle of elevation from all the places on Earth.

Question 6. State the similarities and dissimilarities between dwarf planets and satellites.
Answer:

The similarities between dwarf planets and satellites are as follows

1. Size: Both dwarf planets and satellites are satellites relatively small in size.
2. Light and heat: Neither dwarf planets nor satellites emit light or heat of their own.
3. Movement: Both have rotation and revolution.

The dissimilarities between dwarf planets and satellites are as follows

1. Revolution: The dwarf planets revolve around the Sun, whereas the satellites do. Revolve around their individual, specific planets of origin.
2. Number: The number of dwarf planets is much less compared to the number of satellites.
3. Path: The revolutionary path of dwarf planets is bigger than the satellites.

Question 7. Why is the Earth considered to be a planet of the solar system?
Answer: The Earth is considered to be a planet of the solar system because of the following reasons

1. Origin: The Earth like all other planets is believed to have originated from the star of the solar system, the Sun.
2. Revolution: Like the other planets of the solar system (such as Venus, and Jupiter), the Earth also revolves around the Sun in its orbit.
3. Heat and light: Like the other planets of Ans The sum of all ecosystems on Earth is the solar system, the Earth too, does not emit any light and heat.
4. Gravitational power: Like the other planets of the solar system, the Earth also has gravitational power.

Question 8. Why has Pluto been classified as a dwarf planet?
Answer: One of the characteristics that define planets is that they have enough gravitational force to dominate their neighbourhoods by clearing up the debris near their orbits. Pluto’s orbit is still somewhat cluttered.

Pluto is just 0.07 times the mass of the other objects in or near its orbit and there are still many objects similar in size to Pluto moving around its orbit. Also, the orbit of Pluto is not well-defined. It at times enters the orbit of Neptune. Moreover, Pluto is the smallest planet in the solar system. It is only about one-tenth of the size of the Earth. Hence, on August 24, 2006, the International Astronomical Union classified Pluto as a dwarf planet.

Question 9. Why is the average distance between the Earth and the Sun not the same throughout the year?
Answer: The Earth revolves around the Sun in an elliptical orbit. As the Sun is located at one of the focus of the ellipse, the distance of the Earth from the Sun varies, during its period of revolution.

The distance of the Earth is maximum on 4 July, when it is 152.6 million kilometres away, and minimum on 3 January, when it is 147.5 million kilometres away from the Sun. If the orbit would have been a perfect circle, the distance between the Earth and the Sun would have remained the same throughout.

Question 10. Give a brief description of the biosphere.
Answer: The sum of all ecosystems on Earth is known as the biosphere. This includes all the parts of the atmosphere, lithosphere and hydrosphere that are suitable for the sustenance of life. Water, sunrays and the proper structure of the atmosphere have made life possible on Earth and have also supported the wide range of flora and fauna.

The range of the biosphere generally extends from a height of 15 km above the Earth’s surface to about 9 km below the sea level in the hydrosphere. Right from the creation of life, various evolutions have taken place in the biosphere that have supported its expansion. To date, the Earth is the only planet in the solar system where the existence of life can be found.

Question 11. How is the Earth unique among all the other planets in the solar system?
Answer: The Earth is unique among all the other planets in the solar system because of the following reasons-

1. It is the largest among all the inner planets.
2. The distance of the Earth from the Sun is exactly suitable for the sustenance of life on Earth.
3. The Earth is the only planet to have water and so is rightly named the ‘Blue Planet’.
4. The rotational and revolutionary movement of the Earth along with its axial tilt of 66% helps to maintain the temperature balance in places all over the Earth.
5. The average temperature on the surface of the Earth is about 15°C, which is suitable for the growth and sustenance of life.

Question 12. Explain what the Earth looks like from space.
Answer: From space, the Earth looks like a blue sphere due to the presence of excess water (about 71%). There are white spots around both Poles because of ice, green spots for the forests and grey spots for the deserts, hills and mountains.

As the predominant colour of the Earth is blue, the Earth appears as a ‘Blue Planet’ from space. But the surface of the Earth seems like a rough terrain because of the presence of mountains, plains and plateaus.

Question 13. How did the Greek scholar Eratosthenes calculate the circumference of the Earth?
Answer: In the third century BC, Eratosthenes was the first person who calculate the size of the Earth, with an assumption that the Earth is a perfect sphere. Eratosthenes observed that on (23%2°N) is exactly vertical at noon. On the same 21 June (Summer Solstice), the Sun in Syene day in Alexandria (30%1⁄2°N), the angle between the sun rays and the vertical line was 7°12′.

Now, 7°12 is (360°/7°12′) = 1/50 part of the circumference of the Earth. Eratosthenes had already calculated the actual distance between Alexandria and Syene, which he found to be the Centre of the Earth’s 5000 stadia. From these, he calculated the circumference of the Earth to be 5000 stadia x 50 = 2,50,000 stadia, or 46,250 km. (But, now the circumference of the Earth has been measured to be 40,075 km.)

Question 14. Write the differences between stars and planets.
Answer:

 

Question 15. What are the differences between planets and satellites?
Answer: The differences between planets and satellites are-

 

Question 15. Difference between planets and dwarf planets?
Answer: The differences between planets and dwarf planets are-

Question 16. Why from the Earth does the Moon appear bigger than all other heavenly objects in the sky, though it is smaller?
Answer: When we look up at the sky, the Moon appears to be the largest object in space. In reality, the Moon is much smaller in size than the other planets, satellites and stars. It is only about 1/50th of the Earth’s size.

However, being the Earth’s only satellite, it is also our nearest neighbour in space. The distance between the Moon and the Earth is only 3,84,400 kilometres. So it appears larger than all other celestial bodies which are much larger but are at greater distances from the Earth.

WBBSE Chapter 1 Earth As A Planet Very Short Answer Questions

Question 1. What is meant by Geodesy?
Answer: Geodesy: Geodesy is a scientific discipline that deals with the different methods of survey and other measurements to study the shape and size of the Earth.

Question 2. What is meant by ‘geoid’?
Answer: Geoid: The word ‘geoid’ is taken from the Greek word ‘genocides’. ‘Geo’ means ‘Earth’ and ‘oeides’ means ‘similar to’. Therefore, geoid means ‘similar to the Earth’ or ‘like the Earth’.

Question 3. Why is the Earth’s equatorial diameter not equal to its polar diameter?
Answer:  Earth’s Equatorial Diameter Not Equal To Its Polar Diameter:- The equatorial region of the Earth experiences centrifugal force and so, it bulges out. On the other hand, the polar regions experience centripetal force and so, are flattened. Therefore, the equatorial diameter of the Earth is not equal to that of the polar diameter.

Question 4. What is meant by horizon?
Answer:  Horizon:- The boundary where the sky seems to meet the ground or the sea is known as the horizon. The higher the observer places himself on a place, the longer the horizon becomes.

Question 5. Which experiment of Magellan proved that the Earth is spherical?
Answer: The Portuguese explorer Magellan, set off on an expedition to circumnavigate the Earth from east to west. After three years, he came back to the same place where he had started. This proved that the Earth is spherical, because, had it not been so, he would not have come back to the same place that he had started from.

Question 6. Where is the Kuiper Belt located?
Answer: The ring of icy bodies that revolves around the Sun beyond the orbit of Neptune is known as the Kuiper Belt. The outer limit of the Kuiper Belt is poorly defined. It contains some big heavenly bodies such as Eris, and Pluto as well as millions of other smaller bodies.

Question 7. What are the effects of centrifugal force on the Earth?
Answer: Effects Of Centrifugal Force On The Earth:- When a spherical object rotates continuously a centrifugal force acts on it. Therefore, the middle part bulges out, and at the same time, the polar areas flatten. The Earth is continuously rotating on its axis from the time of its origin. This is the reason why the Earth has a bulged-out middle part and flattened Poles, i.e., it has developed an oblate spheroidal shape.

Question 8.’Curvature of the Earth’s surface is lesser at the Equator than at the Poles’.—Explain.
Answer: The Earth bulges out at the centre and gets flattened at the Poles. Therefore, the Earth forms an oblate spheroid. Oblate spheroids have varying curvature from north to south. It is observed that the smaller the circle, the greater the curvature. This is why the curvature of the Earth’s surface is lesser at the Equator than at the Poles.

Question 9. Why the gravitational force is more in the polar regions than in the equatorial region?
Answer: The Earth is not a perfect sphere, it is an oblate spheroid. Its equatorial diameter is 12,757 km and its polar diameter is 12,714km, which means there is a difference of 43 km between the lengths of these two diameters. As the Poles are closer to the centre of the Earth than the Equator, the greater gravitational force is exerted on the polar regions.

Question 10. Why an object weighs more at the Poles than at the Equator?
Answer: The regions that are closer to the centre of the Earth experience greater gravitational pull than those farther away from the centre. Since the Earth is an oblate spheroid, the Poles are closer to the centre of the Earth and thus, experience greater gravitational force. As a result, all objects weigh more at the Poles than at the Equator.

Question 11. What is meant by the solar system?
Answer: Solar System: The solar system is the name given to the Sun and the various planets, satellites, comets, asteroids and other heavenly bodies, that are moving around the Sun in their unique and specific orbits.

WBBSE Class 9 Chapter 1 Geography And Environment

Question 12. Name the planets of the solar system.
Answer: The planets of the solar system are

1. Mercury,
2. Venus,
3. Earth,
4. Mars,
5. Jupiter,
6. Saturn,
7. Uranus, and
8. Neptune

Question 13. What is meant by a star?
Answer: Star: A star is a gigantic, self-luminous heavenly body made of burning gases. Other celestial bodies such as planets, satellites, comets and asteroids revolve around a star. For instance, the Sun is the largest star in our solar system.

Question 14. What is meant by a planet?
Answer: Planet: A planet (a word derived from a Greek term that means ‘wanderer’) is a large heavenly body that revolves in a particular orbit around a star. A planet does not radiate heat or light energy from internal nuclear fusion reactions. It receives heat and light from the star that it revolves around. For instance, our Earth is a planet that revolves around its star, the Sun.

Question 15. What is meant by a satellite?
Answer: Satellite:- A satellite is a small heavenly object that orbits or revolves around a planet. Like planets, satellites also do not radiate heat or energy from internal nuclear fusion reactions. All the planets in the solar system have satellites, except Mercury and Venus. For instance, the Moon is a satellite that orbits around its planet, the Earth.

Question 6. What is meant by a dwarf planet?
Answer: Dwarf Planet:- According to the International Astronomical Union (IAU), a dwarf planet is a celestial body that orbits a star, and has enough mass to assume a nearly round shape but can not clear the neighbourhood around its ‘orbit. Also, doesn’t have a well-defined orbit of its own.

Question 7. Why is the Earth called the ‘Blue Planet’?
Answer: Blue Planet:- From space, the Earth appears as a blue ball. About 71% of the Earth’s surface is water. As almost three-fourths of the Earth is covered with water, it appears mostly blue from space. This is why the Earth is known as the ‘Blue Planet’.

Question 8. What is a galaxy?
Answer: Galaxy:- A Galaxy is a huge collection of gaseous clouds, dust, billions of stars and their solar systems, that are held together by gravity. Galaxies are spiral, oval or of various other shapes. The Milky Way is one such spiral. Galaxy to which our solar system belongs.

Question 9. Which are the inner planets of our solar system?
Answer: Inner Planets Of Our Solar System:- The first four planets of our solar system, Mercury, Venus, Earth and Mars are closer to the Sun and they are comparatively small in size. Hence these planets are called inner planets.

Question 10. Which are the outer planets?
Answer: Outer Planets:- The last four planets of our solar system i.e., Jupiter, Saturn, Uranus and Neptune are the farthest planets from the Sun. These planets are called outer planets. The orbits of these planets are lying outside the asteroid belt and the size of these planets is comparatively larger than the rest of the planets of our solar system.

Question 11. What is meant by GPS?
Answer: GPS: The Global Positioning System (GPS) is a radio-based navigation system that provides three-dimensional coverage of the Earth in any weather condition. To date, it is the only system which can show one’s exact position on Earth time and anywhere.

Question 12. In which part of the world did GPS first come into use?
Answer: GPS was first developed and implemented in the USA in the 1970s by the US Department of Defence and was used only for military purposes.

Question 13. What information can be gathered from a GPS receiver?
Answer: The information that can be gathered from a GPS receiver are

1. A GPS receiver operated by a user on Earth measures the time taken by the radio signals to travel from four or more satellites to its location. Once the receiver calculates its distance from the satellites, it can figure out the exact position of the user by determining the latitude, longitude and altitude.
2. A GPS receiver also displays the time. GPS satellites have atomic clocks that show accurate time.

WBBSE Chapter 1 Earth As A Planet Match The Column

1.

Answer:  1-C, 2-B, 3-D, 4-A .

2.

Answer:  1-C, 2-A, 3-D, 4-B .

3.

Answer: 1-C, 2-D, 3-B, 4-A .

4.

Answer: 1-D, 2-A, 3-B, 4-C.

Chapter 1 Earth As A Planet Write ‘True’ Or ‘False’ 

1. The shape of the Earth is geoid True

2. The average diameter of the Earth is 12,800 kilometres False

3. The Earth’s orbit is elliptical True

4. If the Earth were a flat plane, sunrise and sunset would occur at the same time at every place on Earth True

5. The weight of any object is always lesser at the Poles False

6. The shape of the Earth is an oblate spheroid because of centrifugal force True

7. The gravitational force acting on the city of Paris is stronger than that at the Cayenne Islands True

8. The Pole Star can be seen even from the southern hemisphere False

9. The Pole Star is located at an angle of 90° from the Equator False

10. The gravitational force acting on the Earth is the same at all latitudes False

11. Lapland city is situated at 60°N latitude False

12. The angle of elevation of the Pole Star increases at 1° if one moves 69 miles or 111km from the pole towards the equator False

13. The Moon does not have any light of its own. True

14. The Earth, along with other planets, moves around the Sun.[true]True

15. The Earth is the only planet in the solar system known to support life.[true]True

16. Stars do not have the light of their own.[flase]

17. Artificial satellites are used to gather information for use by GP True

18. The main control system of GPS is in the United States of Americ a.True

19. According to Eratosthenes, the circumference of the Earth is 2,50,000 stad ia.True

20. Eris is a planet. False

21. Planets are smaller than dwarf planets. False

22. The southern hemisphere has a greater percentage of landmass. False

23. Mercury’s shape is like that of the Earth. False

24. The Earth’s circumference was calculated by Ptol emy.False

25. The average circumference of the Earth is about 40,000 km. True

26. With the help of GPS, we have come to know the exact shape of the Earth. True

27. The Earth’s orbit is 960 million km and its shape is circ ular.False

28. Jupiter has two satellites. False

29. The dwarf planet Eris has 10 satellites. False

30. It is because of the presence of the atmosphere that only the white ray from the Sun reaches the Earth’s su rface.True

31. The Earth and other planets move around the Sun due to the effect of gravitational force.True

32. The biosphere is extended up to 15 km altitude in the atmosphere. True

33. The farthest planet in the solar system iIs Pluto.False

34. The planet Jupiter completes one revolution around the Sun in  12 years.False

35. There are distinct several rings surrounding Mars. False

36. Pluto is a dwarf planet. True

WBBSE Chapter 1 Earth As A Planet Fill In The Blanks

1. The first person to calculate the circumference of the Earth was Eratosthenes

2. In terms of size, the Earth stands fifth among the planets of the solar system.

3. The Sun is 1.3 million times larger in size than the Earth.

4. The only satellite of the Earth is the Moon

5. The Moon is at a distance of about km 3,84,400 from the Earth.

6. The Sun and the heavenly objects that revolve around it are together known as the solar system

7. The satellites used for GPS are generally at a distance of 20,200 km from the Earth’s surface.

8. The person who first succeeded in estimating the volume of the Earth was Aristotle

9. One stadia is equal to 185 metres.

10. The Earth app in colour from the space

11. Eratosthenes estimated the circumference of the Earth based on the angle of incidence of the Sun’s rays.

12. The planet closest to the Sun is Mercury

13. The largest planet in the solar system is Jupiter

14. The movement of the Earth around the Sun is called its revolution

15. Jupiter has 67 satellites.

16. The Earth’s equatorial diameter is greater than its polar diameter.

17. The Earth is divided equally into 360 lines of longitude.

18. The Earth is an oblate spheroid.

19. Magellan started his expedition from the city of Seville in Spain.

20. Aristotle was the first person to observe that the Earth was round after observing the relative position of some stars.

21. The Bedford Canal Experiment proves that the Earth is spherical

22. The [North/ Pole ] Star is visible from any point in the northern hemisphere.

23. The Earth’s North and South Poles are slightly flattened

24. The Earth’s equatorial diameter is 12,757 km.

25. The Earth’s polar diameter is 12,714 km.

26. In the year 1671, Jean Richard conducted the pendulum experiment.

27. In ancient Greek civilisation people thought that the Earth was flattened

Chapter 1 Earth As A Planet Answer In One Or Two Words

Question 1. How many true planets are there in the solar system?
Answer: 8.

Question 2. What is the area of the Earth’s surface?
Answer: Almost 510.72 million sq km.

Question 3. Name two planets that do not have satellites.
Answer: Mercury and Venus.

Question 4. Which planet has the most number of satellites?
Answer: Jupiter.

Question 5. What is the estimated mass of the Earth?
Answer: 5.97219 x 1024 kg.

Question 6. How much time does the light of the Sun take to reach the Earth?
Answer: 8.2 minutes.

Question 7. What was the circumference of the Earth according to Eratosthenes?
Answer: 46,250 km.

Question 8. Name one Jovian planet.
Answer: Mars.

Question 9. What is the only source of light in the solar system?
Answer: Sun.

Question 10. What is the full form of GPS?
Answer: Global Positioning System.

Question 11. How can the planets of the solar system be classified?
Answer: Planets and dwarf planets.

Question 12. What are the two satellites of Mars?
Answer: Fobos and Demos.

Question 13. What is the minimum number of satellites required to operate GPS?
Answer: 3.

Question 14. Name the three major components of GPS.
Answer: The space segment, the control segment and the user segment.

Question 15. Which planet was designated as a dwarf planet in 2006?
Answer: Pluto.

Question 16. Which heavenly body is at the centre of the solar system?
Answer: The Sun.

Question 17. Which planet is known as the ‘Red Planet’?
Answer: Mars

Question 18. Which heavenly body is the source of light in the solar system?
Answer: Sun

Question 19. What is the greatest distance between the Sun and the Earth?
Answer: 152.6 million km.

Question 20. In which direction does the Earth rotate?
Answer: West to east.

Question 21. What is the full form of IAU?
Answer: International Astronomical Union.

Question 22. Which cities of Egypt had Eratosthenes chosen to calculate the circumference of the Earth?
Answer: Syene and Alexandria.

Question 23. Where was the General Assembly of the IAU held on August 24, 2006?
Answer: Prague, the capital of the Czech Republic.

Question 24. Which is the largest planet in the solar system?
Answer: Jupiter.

Question 25. From when did GPS become operational?
Answer: From the 1990s.

Question 26. Where on the Earth’s surface is the main control system of GPS located?
Answer: Colorado, USA.

Question 27. Till what depth in oceans are organisms found?
Answer: 9 km

Question 28. From where do living organisms get the oxygen required for their survival?
Answer: The atmosphere.

Question 29. What is the average temperature of the Earth?
Answer: 15° C.