WBBSE Class 6 Geography Solutions Chapter 2 Shape of The Earth

Detailed explanations in West Bengal Board Class 6 Geography Book Solutions Chapter 2 Shape of The Earth offer valuable context and analysis.

WBBSE Class 6 Geography Chapter 2 Question Answer – Shape of The Earth

Objective Type Questions :

Question 1.
What is the shape of the Earth?
Answer:
An oblate spheroid.

Question 2.
What is the equatorial diameter of the Earth?
Answer:
12,757 km.

Question 3.
What is the polar diameter of the Earth?
Answer:
12,714 km.

Question 4.
Who was the first sailor to circumnavigate the Earth?
Answer:
Magellan.

Question 5.
Who was the first Greek philosopher to prove that Earth is spherical?
Answer:
Aristotle.

Question 6.
Who was the first scientist to prove that Earth is a spheroid?
Answer:
Newton.

Question 7.
Who was the first geographer who attempt to measure the size of the Earth?
Answer:
Eratosthenes.

Question 8.
Who was the first Indian Astronomer to describe the Earth as sphere?
Answer:
Aryabhatta

Question 9.
Which eclipse gives the evidence that the Earth is round?
Answer:
Lunar Eclipse.

Question 10.
What is the equatorial circumference of the Earth?
Answer:
40,077 km.

Question 11.
What is the polar cicumference of the Earth?
Answer:
40,009 km.

Question 12.
How much part of the Earth is covered with water?
Answer:
71%.

Question 13.
Which one of the earliest proofs of the Earth’s sphericity, is the most conclusive and practical?
Answer:
Shadow of the Earth at Lunar Eclipse.

Question 14.
What do you understand by the term ‘oblate spheroid’?
Answer:
A sphere with unequal diameter.

Question 15.
Which force creates a bulge at the equatorial region?
Answer:
Centrifulgal force.

Question 16.
Where is Bedford level canal located?
Answer:
In UK.

Question 17.
Who was the scientist to perform Bedford level canal experiment?
Answer:
A.R.Wallace.

Question 18.
What is the difference between polar diameter and equatorial diameter of the Earth?
Answer:
43 km.

Define and give very short answer of the following briefly 2 marks each

Question 1.
What is a spheroid ?
Answer:
A spheroid is not a perfect sphere. It is a sphere of rotation.

Question 2.
What is Geoid ?
Answer:
Geoid means Geo+oid. It means Earth shaped i.e., a spheroid.

Question 3.
What is centrifugal force ?
Answer:
A force which acts away from the centre of a circle.

Question 4.
What is Horizon ?
Answer:
Horizon is the line where Earth and sky seem to meet.

Question 5.
What do you mean by Geocentric?
Answer:
In olden days, it was believed that the Earth is the centre of Solar System.

Question 6.
What is heliocentric ?
Answer:
It means the idea that Sun is the centre of the Solar System.

Question 7.
What is circumnavigation ?
Answer:
To sail round the Earth without changing direction.

Question 8.
Explain the spherical hori-
Answer:
Where Earth and sky appear to meet. It always look spherical due to spherical Earth.

Question 9.
How does circumnavigation determine the Earth’s shape?
Answer:
Because it is possible to circumnavigate only the spherical Earth.

Question 10.
How do aerial photographs zon. help ?
Answer:
The photographs taken from space show spherical Earth.

Question 11.
Why is the shape of the Earth described as oblate spheroid?
Answer:
Because it is flattened at the poles and bulging at the equator.

Answer the following questions briefly : 3 marks each

Question 1.
Name the ancient Geographers and their views regarding shape of the Earth.
Answer:
In olden days, it was believed that the Earth is the centre of Solar System. To a common man, Earth appeared as a flat disc. Anaximander took it as cylindrical, Aristotle, Ptolemy, Aryabhatta and Pythagoras gave proofs that Earth is a sphere.

Question 2.
Name some modern Geographers and their views about shape of the Earth.
Answer:
(a) Magellan, after circumnavigation of the Earth, showed it to be a sphere.
(b) Copernicus proved that the Earth moved round the Sun.
(c) Galileo proved spherical shape of the Earth.
(d) Newton proved Earth to be a spheroid.

Question 3.
Why does the Sun not rise at the same time everywhere in the world?
Answer:
If the Earth were flat, the whole world would have the sunrise and sunset at the same time. As the Earth is spherical and rotates from West to East, places in the East see the Sun earlier than the places in the West.

Question 4.
“The whole of the approaching ship is not visible at one time.” Why ?
Answer:
Along its curved surface, the appearance of a ship is gradual. We see first the smoke, then the mast and then the hull. If the Earth were flat, the entire ship would be seen all at once.

Question 5.
How can you prove that the Earth is a shape by looking at the Pole Star ?
Answer:
The Pole Star is at an angle of 90° at the North Pole. Its angle decreases towards the equator. It can happen only in an arc of a circle on surface of a sphere.

Question 6.
Briefly describe the shape of the Earth.
Answer:
The Earth is not a perfect sphere. Due to its rotation on its axis, the shape of Earth is bulging at equator and flattened at poles. It is a spheroid.

Question 7.
How did Earth get its atmospheric blanket?
Answer:
From the rotating cloud of gas and dust, heavy elements were separated. The remaining cloud of gases formed the atmosphere and functions as a blanket.

Question 8.
“Even when the Earth is spherical, if appears to be flat.” Discuss.
Answer:
The actual shape of the Earth is spherical. The curvature of the Earth is small as compared to its big size. For a small area upto 100 sQuestion mile, this curvature is negligible. Therefore, it appears flat.

Question 9.
Why is the Earth slightly flattened at the poles ?
Answer:
The Earth is not a perfect sphere. It is slightly flattened at both the poles. It is due to the centripetal force produced by the rotation of the Earth.

Question 10.
Why does the Earth have an equatorial bulge?
Answer:
The rotation of the Earth produces centrifugal force acting outwardly on the surface of the Earth. Thus, the equatorial parts are pulled away from the centre. With the result, equatorial circumference is longer than the polar circumference by 125 km.

Question 11.
What is the latest and most convincing proof of the Earth’s spherical shape ?
Answer:
Photographs of the Earth have been taken by Apollo-astronauts from high altitudes. These give a true perspective view of the curvature from outer space. These show clearly the curved edge of the Earth. This is the most convincing proof.

Answer the following questions : 5 marks each

Question 1.
(a) Which Eclipse provides evidence to show a spherical Earth ?
(b) Who was the first scholar to provide this evidence?
(c) How did he prove that the Earth is a sphere ?
Answer:
(a) The lunar eclipse proves that the Earth is a sphere
(b) Aristotle was the first scholar to show this.
(c) The shadow cast by Earth on the Moon during the lunar eclipse is circular. Only a spherical Earth casts a circular shadow.

Question 2.
State four traditional proofs of the Earth’s spherical shape.
Answer:

1. The shadow cast by Earth on the Moon during a lunar eclipse is always circular.
2. The Sun, planets and other heavenly bodies are spherical in shape.
3. The Sun rises and sets at different times in different places due to curvature of the Earth.
4. Circumnavigation round the Earth is a proof of its spherical shape.

Question 3.
(a) Who was the first geographer to measure the circumference of the Earth ?
(b) What observations did he make?
(c) How did he calculate the circumference of the Earth?
Answer:
(a) In olden days, man was unable to determine the size of the Earth due to his limited knowledge. About 2000

years ago (in 230 BC) an Egyptian astronomer, Eratosthenes made the first attempt to measure the circumference of the Earth.

(b) He assumed that the Earth was a sphere. On 21st June, he observed at Syene (Aswan) in Egypt that the Sun was directly overhead at that place. At Alexandria, on the same day, the Sun was not directly overhead at noon. It was 7° 12 minute away from the vertical. Eratosthenes measured the distance between Syene and Alexandria. It was found to be 5000 stadia (925 km).

(c) Thus, assuming that the Earth’s circumference measured 360°, he calculated the circumference of the Earth.
7.2° angle on the circumference = 925 km
1° angle on the circumference = \(\frac{925 \times 10}{72}\) 360° angle on the circumference
= \(\frac{925 \times 10 \times 360}{72}\) = 46,250 km
This measurement was very close to the modern accurate measurement of 40,000 km.

Question 4.
Describe any three experiments to prove the Spherical Shape of the Earth.
Answer:
(i) If you observe a ship approaching sea coast, the top of the mast is seen first and the hull, lower parts are seen gradually. Due to the curvature of the Earth, the whole ship is not seen at one time.

(ii) Fix three poles of equal length at equal distance on the ground. These do not give a horizontal level. The top of the middle pole looks higher than the other two poles due to the curvature of the Earth. This experiment was done by Mr. A.R. Wallace on Bedford canal.

(iii) If you look around at the Earth’s horizon (where Earth and sky appear to meet), it will everywhere and always appear circular. It widens with increasing altitude due to Spherical Earth.

Question 5.
What is the shape of the Earth ?
Answer:
Nowadays, scientific knowledge and observations have proved that the Earth is spherical in shape. But the actual mea-
surements of Earth’s dimensions have revealed that Earth is not a perfect sphere. It is slightly bulging at the equator and flattened at both the poles. It is an oblate spheroid. Its equatorial diameter is longer than its polar diameter by 43 km.

Question 6.
What is ‘Geoid’ ?
Answer:
The Earth has a unique shape. It is not similar to anything. A special term ‘Geoid’ is used to describe the shape of the Earth. It means ‘Earth shaped’. It is a combination of two words (Geo+oid) and it means a shape identical to spheroid shape of the Earth.

Identify the correct answers 1 mark each

Question 1.
The average radius of the Earth is
(a) 5400 km
(b) 6,400 km
(c) 7,400 km
(d) 8,400 km
Answer:
(b) 6,400 km

Question 2.
The shape of the Earth is like the
(a) Cylinder
(b) Mango
(c) Pear
(d) Apple
Answer:
(c) Pear

Question 3.
Eratosthenes calculated the circumference of the Earth to be about.
(a) 1,52,000 stadia
(b) 2,52,000 stadia
(c) 3,52,000 stadia
(d) 4,52,000 stadia
Answer:
(b) 2,52,000 stadia

Question 4.
Greek philosopher and mathematician Pythagoras (572-500 B.C.) was among the first to suggest that the shape of the Earth was
(a) like a globle
(b) like a box
(c) like a cylinder
Answer:
(a) like a globe

Question 5.
From the space, the Earth looks
(a) black
(b) brown
(c) red
(d) blue
Answer:
(d) blue

Question 6.
During a lunar eclipse, the shadow of the Earth on the Moon appears as
(a) a straight line
(b) an arrow
(c) a box
(d) an arc of a circle
Answer:
(a) an arc of a circle

Question 7.
Due to sphere shape of the Earth, the Pole star at the North Pole can always be observed at
(a) 30° in the sky
(b) 60° in the sky
(c) 90° in the sky
(d) 180° in the sky
Answer:
(c) 90° in the sky

Question 8.
Megallan, the Portuguese explorer sailed completely around the Earth and returned to his starting point is
(a) Britain
(b) Spain
(c) Japan
(d) France
Answer:
(b) Spain

Question 9.
As one travels southwards, an angle of Pole star (North pole)
(a) increases
(b) decreases
(c) remains same
(d) becomes zero
Answer:
(d) decreases

Fill in the blanks with correct words 1 mark each

1. Polar circumference of the Earth is less than _______.
Answer:
Equator

2. The Earth bulges a little at the and is flattened at the _______.
Answer:
Equator

3. The shape of the Earth is described by scientists, have truely given the name ‘geoid’ meaning ‘_______’ or ‘_______’.
Answer:
Earth-shaped/Earth like form

4. During lunar eclipse shadow of _______ and its curvature can be observed with naked eye.
Answer:
Earth

5. The polar diameter of the Earth is _______.
Answer:
12,714 km

6. A Greek philosopher and scientist named _______ was the first to declare that the Earth is round.
Answer:
Aristotle

If the sentence is true, write ‘T’ and if false write ‘F’ against the following 1 mark each

1. If the earth was flat the pole star would have the same height for all latitudes.
Answer:
True

2. The height of the pole star in the sky varies with the latitude.
Answer:
True

3. When three ships are approaching the shore, the observer first see only one ship. The others lie below his line of vision.
Answer:
True

4. During an eclipse of the Moon, the shadow of the Earth which is thrown on the Moon, is always straight line.
Answer:
False

5. If the Earth was flat, the rising Sun would be seen at all places at the same time.
Answer:
True

6. Due to spherical shape of the Earth, places in the east see the rising Sun earlier.
Answer:
True

Shape of The Earth Class 6 WBBSE Notes

Earth : A unique planet. The Earth is a unique planet (Watery planet or Blue planet) because it is the only planet on which life exists.

Shape of the Earth : In olden days, people regarded the Earth as a plane surface, i.e., flat. But Anaximander, Aristotle, Ptolemy, Aryabhatta and Pythagoras gave proofs to show the Earth as a sphere.

Modern Views : Modern views confirm the spherical shape of the Earth, Magellan, Galileo, Copernicus, Newton proved the Earth to be a spheroid, i.e., a sphere of rotation. The Earth has the shape of Geoid. It is flattened at the poles and bulging at the equator.

Size of the Earth : An Egyptian Astronomer, Eratosthenes (230 BC) was the first to measure the size of the Earth. The equatorial diameter is 1,22,756 km. while polar diameter is 12,713 km.

In the old days, the Earth was considered to be a flat disc with steep edges. It was also thought that all heavenly bodies revolved around the earth. Early ideas of Universe were influenced by religious thoughts and practices. The Hindus believed that Universe was shaped like an egg-Brahmanda. According to Vedas, Earth was flat circular with a heaven above. Aryabhatta, the famous Indian astronomer, however, believed that the earth was spherical in shape and rotated on its axis. In Europe, the Greek philosopher Pythagoras was the first to state that the Earth was spherical in shape, there was considerable opposition to this idea in those days.

Nowadays, scientific knowledge and observations have proved that the Earth is spherical in shape. But the actual measurements of Earth’s dimensions have revealed that Earth is not a perfect sphere. It is slightly bulging at the equator and flattened at both the poles. It is an oblate spheroid.

The Earth is not flat –

If the Earth were a flat disc, then the rising Sun would have been seen at all places at the same time. This does not happen. Places in the east see the rising sun earlier.

When a ship approaches land, its funnel or mast is seen first and then the full. If the Earth had been flat, the whole ship would have been seen at one time.

The Earth is a sphere : Proof of sphericity of the Earth (How did we discovered the Earth is round?)
Several things show that the shape of the Earth is rounded or sphere.

Indirect Proofs –

Sunrise and Sunset : The Sun does not rise at the same time in every country. It rises in London, for example, some 5 hours later than in Mumbai. If the Earth were flat, the sunrise would be everywhere at the same time.

Sighting a ship : An observer watching through a telescope the approach of a ship seas first the smoke then the funnels, and then the hull. If the Earth were flat we would see the whole of the ship at one time. This proofs the rounded shape of the Earth.

The Earth’s shadow: The shadow cast by the Earth on the Moon during the lunar eclipse is circular. Only a round body can cast a circular shadow. All heavenly bodies like the Sun, Moon and other planets appear circular in all positions. The Earth and other heavenly bodies must be rounded and spherical in shape.

Travelling Round the Earth: As the Earth is spherical in shape, it is possible to circumnavigate the Earth. Magellan was the first to go round the Earth in a ship and complete his voyage without encountering a sharp edge. An aeroplane can fly round the world. If we travel continually in the same direction, we return eventually to our starting point.

The Bedfort Level

Experiment: An experiment was made many years ago in the Bedford Level Canal area in Britain. A.R. Wallace did this experiment. The water level of the canal provided the base of measurement. Three poles were fixed at intervals of about 5 km. such that the poles were rising to the same height about the level of water in the canal.

When a telescope was placed that in such a way that the top of pole A was in line with of pole C, it was found that the line of sight was intersecting the middle pole B. This would not happen if the Earth were flat. The middle pole B appeared higher owing to the curvature of the Earth.

The spherical horizon : The limit of the horizon at a place is circular and the horizon widens as the height of the observer increases. This again indicates the spherical shape of the Earth.

Effect of gravity : The weight of a substance is related to the effect of force of gravity on that substance. It is found that an object weighs nearly the same at all places on the Earth. This means that the force of gravity is nearly equal to all places. This is possible only when the Earth is a sphere.

Position of the pole star : The pole star appears vertically overhead at the North Pole. If the Earth were flat, the pole star should be overhead at all places on the Earth.

This is not the ease. The angle of elevation of the pole star is about 40° at London and 0° at Singapore or on equator. This is possible only when the earth is spherical in shape.

Direct Proofs –

Aerial Photographs : The most clinching evidence of the spherial shape of the Earth is obtained from photographs taken from space. Pictures taken by satellites show the spherical shape of the Earth. The astronauts from the moon have taken pictures of the Earth showing its spherical shape.

Artifical Satellites: Artificial Satellites and many space probes are put in orbit on the assumption that the Earth is spherical. The calculations have proved correct and the space probes of other planets of the Solar System have provided valuable data.

Earth as an Oblate Spheroid –

Definition of Oblateness of the Earth : A sphere which is slightly flattened at two opposite ends is called an oblate spheroid or oblate ellipsoid. The Earth is not, in fact, a perfect sphere, it has an equatorial bulge and a polar flattening. This type of spherical shape is known ‘oblate spheroid’.

Proofs of the Oblateness of the Earth –

Difference between the length of the Equatorial diameter and Polar diameter:

The Earth has got an equatorial diameter of 12,757 km. through east-west and a polar diameter of 12,714 km. through north-south. In length the equatorial diameter is larger than the polar diameter by 43 km. Hence there is a slight bulging at the equator and a flattening at the two polar regions. This is caused by the rotation of the Earth.

Length of circumferences : The length of equatorial circumference is 40,076 km and the polar circumference is 40,009 km. The legnth of equatorial circumference is larger than the polar circumference by 67 km. Thus the Earth has got a shape of an oblate spheriod.

Concept of Geoid : Earth is not a perfect sphere. It is also not a simple oblate spheroid. A study of satellite orbits has already revealed that the Earth is not a perfect oblate ellipsoid or a perfect sphere as it was previously thought to be.

The high mountains like Himalayas or deep valleys are also just a dot when we consider the size of the Earth. The Earth ‘bulges out’ a little at the equator and is flattened at the poles. There are much bigger depressions and bumps on its surface.

These are areas of low atmospheric pressure which produce climatic changes. In as much as Earth is unique, its shape is also unique. Scientists have truly given the name ‘geo’ to this form or ‘geoid’ meaning ‘earth like form’ or earth shaped.