# Chapter 2 – Movements of the Earth | Class 9 School Geography Solution

 Book Name : School Geography Subject : Geography Class : 9 (Madhyamik) Publisher : Bengal Book Syndicate (P) Ltd. Chapter Name : Movements of the Earth

Question 1 (a)

Ancient people believed that the Sun / Earth / Mars / Jupiter was at the center of the Solar System.

Ancient people believed that the Earth was at the center of the Solar System.

Question 1 (b)

Venus and Uranus / Mars and Earth / Jupiter and Saturn / Uranus and Neptune spin about their axes in a clockwise direction.

Venus and Uranus, along with their moons, are known to spin about their axes in a retrograde or clockwise direction.

Question 1 (c)

The speed of rotation at the equator is about 1650 Km./1670 Km./1634 Km./1790 km. per hour.

The speed of rotation at the equator is about 1670 Km.

Question 1 (d)

Winds and ocean currents deflect to their right / left / upside/downside in the Southern Hemisphere.

Winds and ocean currents deflect to their left in the Southern Hemisphere due to the Coriolis effect.

Question 1 (e)

The imaginary line that separates the lighted half from the darkened half of the Earth is called the twilight/dawn/shadow circle/dusk.

The imaginary line that separates the lighted half from the darkened half of the Earth is called the shadow circle.

Question 1 (f)

The deflective effect of Earth’s rotation was discovered by Foucault/Coriolis/ Galileo/Copernicus.

The deflective effect of Earth’s rotation was discovered by Coriolis.

Question 1 (g)

The Earth’s axis remains inclined at an angle of 23½° / 45½° / 66½° / 15° to the plane of orbit.

The Earth’s axis remains inclined at an angle of 23½° to the plane of orbit.

Question 1 (h)

The Earth takes 24 hours/28 days/365¼ days/375¼ days to complete one revolution.

The Earth takes approximately 365¼ days to complete one revolution around the sun.

Question 1 (i)

On July 4/August 17/January 3/February 5 the Earth is the farthest from the Sun.

On July 4, the Earth is the farthest from the Sun, a phenomenon is known as aphelion.

Question 1 (j)

On 23rd September/22nd December/24th May/ 15th June days and nights are equal all over the Earth.

On 23rd September, days and nights are equal all over the Earth. This day is known as the autumnal equinox in the Northern Hemisphere and the vernal (spring) equinox in the Southern Hemisphere.

## If the sentence is true write T and if false write F against the following

Question 2
1. Our Earth has two movements namely Rotation and Revolution.
2. The speed of Earth’s rotation increases from the equator towards the poles.
3. As the Earth rotates from east to west, the sun appears to move from west to east.
4. Dawn is the period or time of the day before sunrise.
5. The Coriolis concept was developed by Scientist Foucault.
6. The Earth’s axis always points to the North star in the Northern Hemisphere.

1. True
2. False; the speed of rotation is greater at the equator than at the poles.
3. True
4. True
5. False; although it was named after Gaspard-Gustave de Coriolis.
6. False; the Earth’s axis points towards the direction of the North Star, but not always directly at it.

## Fill in the blanks with appropriate words

Question 3
1. The orbit of the Earth is ____ in shape.
2. A leap year has ____ days.
3. The average distance between the Sun and the Earth is ____.
4. The region beyond the ____ ____ is popularly known as the ‘Land of Midnight Sun’.
5. Summer Solstice is on ____ ____.
1. elliptical
2. 366
3. 93 million miles
4. Arctic Circle
5. June 21st/22nd

## Answer in word or words

Question 4 (a)

When is it winter solstice in the Northern hemisphere?

Winter solstice occurs in the Northern Hemisphere around December 21st.

Question 4 (b)

What does rotation of the Earth cause?

The rotation of the Earth causes day and night.

Question 4 (c)

What is the speed of revolution of the Earth?

The speed of revolution of the Earth around the Sun is about 29.78 km/s.

Question 4 (d)

How far away is the Earth from the Sun on Aphelion?

The Earth is about 94.5 million miles away from the Sun at Aphelion.

Question 4 (e)

What is the colourful light seen in the dark nights at the South Pole called?

The colourful light seen in the dark nights at the South Pole is called the Aurora Australis or Southern Lights.

Question 5 (a)

State Foucault’s proof on Earth’s rotation in short.

Foucault’s pendulum is a device used to demonstrate the rotation of the Earth. When the pendulum swings back and forth, the plane of its swing appears to rotate slowly clockwise or counterclockwise (depending on the location) over the course of a day. This is due to the rotation of the Earth underneath the pendulum. By observing the rotation of the pendulum, Foucault was able to prove that the Earth rotates on its axis.

Question 5 (b)

What is Summer Solstice?

Summer Solstice is an astronomical event that occurs each year between June 20th and 22nd in the Northern Hemisphere (and between December 20th and 23rd in the Southern Hemisphere). It is the longest day of the year and the day with the most hours of daylight.

Question 5 (c)

Since the earth is round, one half or the earth receives sunlight and remains illuminated, while the other side does not get sunlight and remains dark. The imaginary line of longitude which is the dividing line between the illuminated and the darkened portions of the earth is known as the Shadow circle or circle of illumination.

Question 5 (d)

What is Aphelion ?

Aphelion refers to the point in the orbit of a planet or other celestial body when it is farthest away from the Sun. In the case of the Earth, the Aphelion occurs around July 4 each year, when the Earth is at its greatest distance from the Sun.

Question 5 (e)

What is Aurora Borealis?

Aurora Borealis, also known as the Northern Lights, is a natural light display that occurs in the polar regions of the Earth, predominantly in the Arctic. It is caused by the interaction between charged particles from the Sun and the Earth’s magnetic field and atmosphere.

Question 5 (f)

What do you mean by Equinox?

Equinox is an astronomical term that refers to the two points on the Earth’s orbit around the Sun when the day and night are approximately equal in length. The word “equinox” comes from the Latin words “aequus” and “nox,” which mean “equal” and “night,” respectively.

Question 6 (a)

State the comparison between summer and winter solstices.

Comparison table between summer and winter solstices:

Summer Solstice Winter Solstice
Around June 21 Around December 21
The longest day of the year The shortest day of the year
Sun is highest in the sky  Sun is Lowest in the sky
Northern Hemisphere affected Southern Hemisphere affected

Question 6 (b)

Mention three differences between the rotation and revolution of the Earth.

Comparison table between rotation and revolution of the Earth:

Rotation Revolution
Spinning of the Earth around its axis Movement of the Earth around the Sun
One day (24 hours) One year (365.25 days)
Causes day and night, and the apparent movement of the Sun Causes the changing of seasons and the variation in the length of daylight and darkness

Question 6 (c)

What do you mean by the revolution of the Earth?

The revolution of the Earth refers to its movement around the Sun in an elliptical orbit. The Earth takes approximately 365.25 days or one year to complete one revolution around the Sun. This movement causes the changing of seasons and the variation in the length of daylight and darkness.

Question 6 (d)

Write two effects of Earth’s rotation.

Here are two effects of Earth’s rotation:

1. Day and night: The rotation of the Earth causes the alternation of day and night. As the Earth rotates on its axis, different parts of the planet are exposed to the Sun’s light, while other parts are in shadow.
2. Apparent movement of the Sun and stars: The rotation of the Earth also gives the impression that the Sun and stars are moving across the sky, even though they are actually stationary. This is because as the Earth rotates, it causes different parts of the sky to come into view, while others move out of view.

Question 6 (e)

When does summer solstice occur in the Southern Hemisphere?

The summer solstice occurs in the Southern Hemisphere around December 21 or 22 each year. During the summer solstice, the Southern Hemisphere is tilted towards the Sun, resulting in the longest day of the year and the shortest night. It marks the beginning of the summer season in the Southern Hemisphere.

Question 6 (f)

What are Aphelion and Perihelion?

Aphelion is the point in the orbit of a planet or other astronomical body at which it is furthest from the Sun. The word comes from the Greek words “apo” (away from) and “helios” (Sun).

Perihelion is the point in the orbit of a planet or other astronomical body at which it is closest to the Sun. The word comes from the Greek words “peri” (around) and “helios” (Sun).

Question 6 (g)

Why is 21st March geographically important?

March 21 is geographically important because it marks the occurrence of two important astronomical events – the Vernal Equinox and the Autumnal Equinox, depending on the hemisphere.

• In the Northern Hemisphere, March 21 marks the Vernal Equinox, also known as the Spring Equinox. This is the moment when the Sun is directly above the equator and the length of day and night is almost equal. It also marks the beginning of the spring season in the Northern Hemisphere.
• In the Southern Hemisphere, March 21 marks the Autumnal Equinox. This is the moment when the Sun is directly above the equator and the length of day and night is almost equal. It also marks the beginning of the fall season in the Southern Hemisphere.

Question 6 (h)

How are days and nights caused on Earth?

Days and nights on Earth are caused by the rotation of the Earth on its axis. The Earth rotates once on its axis approximately every 24 hours, which creates a cycle of alternating periods of daylight and darkness.

As the Earth rotates, half of it is facing towards the Sun, experiencing daylight, while the other half is facing away from the Sun, experiencing darkness or night. The line that separates the illuminated half of the Earth from the dark half is called the terminator. The terminator is constantly moving due to the Earth’s rotation, causing the length of daylight and darkness to change throughout the year.

Question 6 (i)

Point out the major causes of change of season.

The major causes of the change of seasons on Earth are:

1. The tilt of the Earth’s axis: The Earth’s axis is tilted about 23.5 degrees relative to the plane of its orbit around the Sun. This means that as the Earth orbits the Sun, different parts of the Earth receive varying amounts of direct sunlight, causing the seasons to change.
2. Revolution of the Earth: The Earth’s revolution around the Sun causes the amount of daylight and darkness to vary throughout the year, which also contributes to the change of seasons.
3. The Earth’s orbit: The Earth’s orbit around the Sun is not a perfect circle, but rather an elliptical shape. This means that at certain points in its orbit, the Earth is closer to the Sun (perihelion) and at other points, it is farther away (aphelion).

Question 6 (j)

Write the different causes for the variation in the lengths of day and night.

The variation in the lengths of day and night are caused by a number of factors, including:

1. The Earth’s axial tilt: The tilt of the Earth’s axis is responsible for the changing seasons and also for the variation in day and night lengths.
2. The latitude of the observer: The length of day and night can also vary depending on the latitude of the observer. At the equator, day and night are roughly equal in length throughout the year, while at higher latitudes the variation becomes more pronounced.
3. The time of year: The length of day and night also varies depending on the time of year. This is because the Earth’s orbit is elliptical, not circular, and the planet moves faster when it is closer to the Sun. As a result, the length of day and night can vary by a few minutes throughout the year.

Question 6 (k)

Why is rotational speed maximum at the equator?

The rotational speed is maximum at the equator because the equatorial circumference is the largest. This means that in order to complete a full rotation in 24 hours, the equator must travel faster than any other latitude.

Question 6 (l)

Is 25th December really a big day or a long day explain?

December 25th is not a big day in terms of being the longest day of the year. In fact, it is typically close to the winter solstice, which is the day with the shortest amount of daylight in the Northern Hemisphere. However, December 25th is a significant day for many cultures and religions, as it is associated with the celebration of Christmas in many parts of the world. The exact significance and celebration of December 25th vary across different cultures and religions, but it is generally considered an important day for many people.

## Give reasons

Question 7 (a)

The Northern Hemisphere has the shortest day on the 22nd of December.

The Northern Hemisphere has the shortest day on the 22nd of December because, on this day, the tilt of the Earth’s axis is at its maximum angle away from the Sun. This causes the Northern Hemisphere to receive the least amount of daylight and experience the longest period of darkness in a day. It marks the Winter Solstice in the Northern Hemisphere, which is the day with the least amount of daylight and the longest night of the year. As the Earth continues to orbit around the Sun, the angle of the tilt of the Earth’s axis gradually shifts, leading to changes in the amount of daylight and darkness experienced in a day.

Question 7 (b)

Days and nights are equal during equinoxes.

During equinoxes, the tilt of the Earth’s axis is not inclined towards or away from the Sun, resulting in equal illumination of both the Northern and Southern Hemispheres. This means that the duration of daytime and nighttime is approximately equal all over the world during the equinoxes.

Question 7 (c)

The inclination of the Earth’s axis has a great impact on seasonal changes on the Earth.

The inclination of the Earth’s axis causes the angle at which the Sun’s rays hit the Earth’s surface to vary, leading to changes in the amount of daylight and the variation in the angle of incidence of sunlight throughout the year. During the summer solstice, the Northern Hemisphere is tilted towards the Sun, resulting in longer days and shorter nights, while the opposite is true during the winter solstice. These changes in daylight and angle of incidence of sunlight also impact weather patterns, with areas receiving more sunlight and daylight tending to be warmer and experiencing more precipitation, while areas receiving less tend to be cooler and drier. This leads to the seasonal changes in temperature and precipitation that are characteristic of different regions on Earth. The variation in the amount of daylight is most noticeable at the poles, where there are periods of continuous daylight and continuous darkness depending on the time of year.

Question 7 (d)

Norway is called ‘the land of midnight Sun’.

Norway is called ‘the land of midnight Sun’ because during the summer months, particularly around the summer solstice, the Sun remains visible for 24 hours a day above the Arctic Circle, which runs through Norway. This phenomenon occurs because of the tilt of the Earth’s axis, which causes the Sun’s path to trace a circular pattern around the Arctic Circle during the summer months, never dipping below the horizon. This creates a period of continuous daylight, where the Sun remains visible even at midnight, hence the name ‘midnight Sun’.

Question 7 (e)

People in Australia celebrate Christmas in summer.

People in Australia celebrate Christmas in summer because December falls during the summer season in the Southern Hemisphere. Since Australia is located in the Southern Hemisphere, it experiences summer during the months of December, January, and February. This is due to the tilt of the Earth’s axis, which causes the seasons to be opposite in the Northern and Southern Hemispheres. So, while people in the Northern Hemisphere experience winter during December, people in the Southern Hemisphere experience summer, making it a perfect time for outdoor activities and celebrations.

## Complete the table

(i) Equator, Equal length of day and night, Spring

(ii) 21st June, Tropic of Cancer, Summer

(iii) 22nd December, Shorter days and Longer nights, Winter

(iv) 23rd September, Equator, Equal duration of day and night

## Long answer or essay-type questions

Question 9 (a)

Explain with diagrams a few proofs to justify that the Earth rotates.

(a) Potter’s wheel experiment: If a potter’s wheel is rotated at a constant speed and a person standing on the wheel drops a ball, the ball will appear to move in a straight line to a person standing next to the wheel. However, to the person on the wheel, the ball will appear to move in a curved path due to the rotation of the wheel. This phenomenon is known as the Coriolis effect and is caused by the rotation of the Earth.

(b) Foucault’s experiment: In this experiment, a long pendulum is suspended from a fixed point and set in motion. Over time, the direction of the pendulum’s swing appears to change, which is due to the rotation of the Earth. This experiment demonstrates the Coriolis effect and provides evidence that the Earth is rotating.

(c) Tower and dropped stone experiment: If a stone is dropped from the top of a tall tower, it falls straight down to the ground. However, if the Earth were not rotating, the stone would fall some distance to the west of the tower due to the Earth’s rotation. The fact that the stone falls straight down provides evidence that the Earth is rotating.

Question 9 (b)

Give at least three proofs supporting the revolutionary movement of the Earth.

Here are three proofs supporting the revolutionary movement of the Earth:

1. Changes in the positions of stars: As the Earth moves in its orbit around the Sun, the positions of stars in the sky appear to change. This is because the apparent position of a star is affected by the position and movement of the observer. Over the course of a year, the positions of stars shift in a predictable manner, which is consistent with the Earth’s revolution around the Sun.
2. The Coriolis effect: The Coriolis effect is the apparent deflection of moving objects (such as air or water) caused by the Earth’s rotation. This effect is responsible for the rotation of hurricanes and the patterns of ocean currents. The direction of the deflection is determined by the direction of the object’s motion and the latitude of the observer. The Coriolis effect is a direct result of the Earth’s rotation.
3. Foucault’s pendulum: Foucault’s pendulum is a device that demonstrates the rotation of the Earth. The pendulum consists of a weight suspended from a long wire that swings back and forth in a fixed plane. As the Earth rotates beneath the pendulum, the plane of its swing appears to rotate in a clockwise direction in the Northern Hemisphere and a counterclockwise direction in the Southern Hemisphere. This is due to the Coriolis effect, which causes the apparent rotation of the pendulum’s plane of swing.

Question 9 (c)

Explain with illustrations and diagrams the effects of Earth’s rotation.

The effects of the Earth’s rotation are as follows:

1. Occurrence of day and night: The rotation of the Earth around its axis causes the occurrence of day and night. As the Earth rotates towards the east, the side facing the Sun experiences day while the side facing away from the Sun experiences night. This phenomenon occurs every 24 hours, which is the time it takes for the Earth to complete one rotation.
2. Apparent daily movement of the sun: Due to the rotation of the Earth, the Sun appears to move across the sky on a daily basis. The apparent daily movement of the Sun is from east to west. This is because the Earth is rotating towards the east, causing the Sun to appear to move towards the west.
3. Determination of direction: The Earth’s rotation also helps in determining direction. The rotation of the Earth causes the apparent movement of the Sun and stars across the sky, which is used to determine direction. For example, the position of the Sun in the sky can be used to determine east and west, while the position of the North Star can be used to determine north.

Question 9 (d)

How does the alteration of day and night take place? Draw a diagram to show this.

The alteration of day and night occurs due to the rotation of the Earth on its axis. As the Earth rotates, one half of it faces towards the Sun, while the other half faces away from it. The side facing the Sun experiences daylight, while the side facing away from it experiences darkness or night.

Here is a simple diagram to show the process:

As the Earth rotates from left to right in this diagram, the side facing towards the Sun experiences daylight, while the side facing away from it experiences darkness. This alternation of day and night continues as the Earth rotates on its axis, completing one rotation every 24 hours.

Question 9 (e)

What do you mean by the ‘Coriolis effect’?

The Coriolis effect is the apparent deflection of the path of any object that moves within a rotating coordinate system. It is a result of the Earth’s rotation and causes moving air and water to appear to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

The Coriolis effect is responsible for many large-scale weather patterns and ocean currents and is also a factor in the movement of objects such as aeroplanes, missiles, and satellites. It plays a crucial role in the study of meteorology, oceanography, and many other areas of science.

Question 9 (f)

What is Earth’s axis? Discuss its significance.

Earth’s axis is an imaginary line that passes through the centre of the Earth and extends from the North Pole to the South Pole. It is tilted at an angle of approximately 23.5 degrees with respect to the plane of the Earth’s orbit around the Sun. The axis is significant because it is responsible for the seasonal changes that occur on the Earth.

The tilt of the Earth’s axis causes different parts of the Earth to receive different amounts of sunlight at different times of the year. When the Northern Hemisphere is tilted towards the Sun, it receives more direct sunlight, resulting in longer days and warmer temperatures. This is the summer season in the Northern Hemisphere. Conversely, when the Northern Hemisphere has tilted away from the Sun, it receives less direct sunlight, resulting in shorter days and colder temperatures. This is the winter season in the Northern Hemisphere.

The axis also determines the length of a day and night at different latitudes. At the equator, where the axis is perpendicular to the Earth’s surface, there are almost equal amounts of daylight and darkness throughout the year.

Question 9 (g)

What are the causes of variation in the lengths of day and night?

The variation in the lengths of day and night is caused by two factors: the tilt of the Earth’s axis and its orbit around the Sun.

1. The tilt of the Earth’s axis: The Earth’s axis is tilted at an angle of approximately 23.5 degrees. This tilt causes different parts of the Earth to receive varying amounts of sunlight throughout the year, resulting in variations in the lengths of day and night. During the summer solstice, the Northern Hemisphere is tilted towards the Sun, resulting in longer days and shorter nights. Conversely, during the winter solstice, the Northern Hemisphere has tilted away from the Sun, resulting in shorter days and longer nights.
2. The orbit of the Earth around the Sun: The Earth’s orbit around the Sun is not a perfect circle, but rather an ellipse. This means that the distance between the Earth and the Sun varies throughout the year. When the Earth is closest to the Sun (perihelion), it travels faster, causing the day to be slightly shorter than when it is farthest away (aphelion).

Question 9 (h)

Describe in brief the effects of the revolution of the Earth with the help of diagrams.

The revolution of the Earth around the Sun causes several effects, which can be demonstrated with the help of diagrams:

1. Seasons: The Earth’s axial tilt of 23.5 degrees causes different parts of the Earth to be tilted towards or away from the Sun at different times of the year. This results in the four seasons of the year: spring, summer, autumn, and winter.
2. Varying lengths of day and night: As the Earth revolves around the Sun, different parts of the Earth receive different amounts of sunlight, depending on the position of the Earth in its orbit. This causes the lengths of day and night to vary throughout the year.
3. The apparent movement of the Sun: As the Earth rotates on its axis, the Sun appears to move across the sky, rising in the east and setting in the west.

Question 9 (i)

Write how changes of seasons take place on Earth.

The changes in seasons on Earth are caused by the tilt of the Earth’s axis and its revolution around the sun. The axis is tilted at an angle of approximately 23.5 degrees. During Northern Hemisphere summer, the North Pole is tilted towards the sun, resulting in longer days and shorter nights, and warmer temperatures. This marks the beginning of summer in the Northern Hemisphere and winter in the Southern Hemisphere. During the autumnal and vernal equinoxes, the Earth’s axis is not tilted towards or away from the Sun, resulting in equal lengths of day and night globally. During Northern Hemisphere winter, the North Pole has tilted away from the Sun, resulting in shorter days and longer nights, and colder temperatures. This marks the beginning of winter in the Northern Hemisphere and summer in the Southern Hemisphere. These changes have a significant impact on the weather patterns and ecosystems across the planet.

## Cross-Word

Clues

Across-

(1) On this day the distance between the Sun and the Earth is the least.

(3) The Sun shines vertically on this during Equinox.

Down-

(2) A natural light display in the night sky in high latitudes.

(4) He proposed that the Sun was at the centre and the Earth moved around It.

(5) The movement of the Earth on its axis.

Across: (1) Perihelion (3) Equator

Down: (2) Aurora (4) Copernicus (5) Rotation

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