# CBSE Class 6 Social Science Geography Revision Notes Chapter 3

## CBSE Class 6 Geography Chapter 3 Notes – Motions of the Earth

Class 6 Geography Social Science Chapter 3 Motions of the Earth discusses how rotation and revolution affect life on Earth. New terms like solstices, equinoxes, orbital planes, Earth’s axis, and so on are introduced.

Class 6 Social Science Geography Motions of the Earth Notes consist of the following important topics.

• Rotation
• Revolution
• Circle of illumination
• Orbital plane
• Leap year
• Elliptical orbit
• Summer solstice
• Winter solstice
• Equinox

### Motions of the Earth Class 6 Geography Chapter 3 Notes

What are the Two Types of Motions of the Earth?

The planet Earth moves in two types of Motions, i.e., rotation and revolution.

• Rotation: When the Earth spins on its axis, this is referred to as rotation. When viewed from the North Pole, it rotates counterclockwise, or from west to east.
• Revolution: The movement of the planet Earth around the Sun in a fixed orbit or path is referred to as a revolution. The Earth also rotates at the same time.

Access Class 6 Geography Chapter 3 – Motions of the Earth Notes

Some Important Definitions

• The Earth’s Axis: An imaginary line forms a 66 1/2° angle with its orbital plane.
• The Orbital Plane: The orbital plane is the plane formed by the orbit.
• Circle of Illumination: The circle of illumination is the imaginary circle on the Earth that divides the Earth into day and night halves. It is not the same as the Earth’s axis and does not coincide with it. The circle of illumination forms a 23 1/2° angle with respect to the Earth’s axis.

Rotation of Earth

The rotation of the Earth causes the phenomenon of day and night. Without rotation, one side of the Earth would be perpetually dark, and temperatures would have dropped in this half. The other half would always stay in daylight, and temperatures would have risen over time. In such cases, life on Earth would be impossible to sustain.

One rotation of the Earth takes 24 hours, which is known as one Day on Earth.

The actual time required to complete one rotation is 23 hours, 56 minutes, and 4 seconds, but it is assumed to be 24 hours.

Revolution of the Earth

• A revolution is the movement of the Earth on its orbit around the Sun.
• The Earth moves in an elliptical orbit around the Sun.
• One revolution takes 365.25 days to complete. This is the time it takes the Earth to complete an elliptical orbit around the Sun.
• A year has 365 days. Every four years, the remaining one-fourth of a day is added up, which results in one extra day. This day is added to the fourth year, which has 366 days. This year is known as a leap year. This day is included in the month of February.
• In a leap year, February has 29 days rather than 28.

Seasons

Seasons change as the Earth’s position around the Sun shifts. A year is divided into summer, winter, spring, and autumn due to changes in the position of the Earth.

Summer Solstice

• Summer Solstice occurs on June 21st in the Northern Hemisphere.
• The Northern Hemisphere faces the Sun on this day.
• Sun rays strike the Tropic of Cancer.
• The North Pole is oriented toward the Sun, and areas North of the Arctic Circle experience six months of continuous daylight.
• The Summer Solstice, which occurs on June 21st, has the longest day and the shortest night.
• The seasons are reversed in the Southern Hemisphere, and it is winter there.

Winter Solstice

• The Winter Solstice occurs on December 22nd in the Northern Hemisphere.
• The Southern Hemisphere is currently tilted towards the Sun.
• The Sun’s rays fall on the Tropic of Capricorn.
• During this time, the Southern Hemisphere has longer days and shorter nights.
• Hence, there are shorter days and longer nights In the Northern Hemisphere.

Equinox

• On March 21st and September 23rd, the Sun’s direct rays fall on the equator.
• Because neither pole is tilted towards the Sun, the entire Earth has equal days and nights.
• On September 23rd, it will be autumn in the Northern Hemisphere, and spring in the Southern Hemisphere.
• On March 21st, it will be spring in the Northern Hemisphere, and autumn in the Southern Hemisphere.

Class 6 Geography Chapter 3 – Motions of the Earth Notes

“Motions of the Earth,” Chapter 3, introduces students to the fascinating concepts of rotation, revolution, various positions of the Earth, and their effects. Needless to say, the chapter contains some key definitions and terms that may be unfamiliar to students. Extramarks’ Class 6 Geography Chapter 3 Revision Notes compile all of these important key points into a single, concise set of notes. They are ideal for exam preparation and revision.

These revision notes are thorough, with detailed explanations of all key concepts. As a result, students do not need to study from multiple study materials. These notes provide a quick review of the chapter. These are curated by subject matter experts, ensuring complete accuracy and factual correctness. As a result, referring to these notes helps students  achieve high scores in exams.

Important Terms Used to Describe Motions of The Earth

To fully comprehend the Earth’s motions, some key terms must be understood.

• The axis of the Earth, also known as the Earth’s axis, is an imaginary pole or line that passes through the centre of the Earth and forms a 66 1/2° angle with its orbital plane. It connects the North and South Poles.
• The plane formed by the orbit is known as the orbital plane.
• On the globe, the circle of illumination separates day and night. The Sun illuminates the Earth, which has a spherical shape. Because of its shape, the Earth only receives half of the Sun’s light at a time, i.e., the portion of the Earth facing the Sun experiences day, while the other half, which is away from the Sun, experiences night. This circle of illumination does not align with the axis of the Earth.
• Earth day is the period of rotation that the planet Earth takes to complete one complete rotation around its axis, which is 24 hours.

What will Happen if The Earth Stops Rotating?

In this case, the portion of the Earth facing the Sun would always have daylight, bringing constant warmth to that region. The other half would always be dark and cold. Life would not be able to exist in such harsh conditions. Thus, the Earth’s motion is necessary for life to exist.

How Long does The Earth Take to Revolve?

The Earth revolves around the Sun in 365 1/4 days (one year). A year is said to have 365 days for the sake of simplicity, excluding the ¼ day or six hours. Over the course of four years, the six hours saved each year add up to one full day of 24 hours. This extra day is then added to the month of February of the following year. Thus, every fourth year, February has 29 days rather than 28 . Such a year with an extra  day, making it 366 days, is known as a leap year.

The Earth orbits the Sun in an elliptical orbit, and it is inclined in the same direction throughout its orbit. This revolution creates four seasons: summer, autumn, winter, and spring. Seasons change in response to changes in the Earth’s orbit around the Sun.

Positions of the Sun

• Summer Solstice: On June 21st, the Northern Hemisphere is at its most tilted position towards the Sun. Because the Sun’s rays fall directly on the Tropic of Cancer, these areas receive more heat. Therefore, the areas near the poles receive less heat. Because the North Pole is inclined towards the Sun, the area beyond the Arctic Circle has continuous daylight for about six months.

As the Sun illuminates the majority of the Northern Hemisphere, it is summer in the regions North of the equator. On June 21, these locations have the longest day and the shortest night. In the Southern Hemisphere, it is the exact opposite. They are in the midst of winter, and the nights are longer than the days.

• Winter Solstice: On December 22nd, the South Pole is in its most tilted position towards the Sun, and the Tropic of Capricorn receives direct sunlight.As the sun’s rays fall directly at the Tropic of Capricorn at 23 1/2° S, they illuminate a large portion of the Southern Hemisphere. As a result, summer in the Southern Hemisphere has longer days and shorter nights. At this time of year, the opposite occurs in the Northern Hemisphere. The 22nd of December has the longest night and the shortest day.
• Equinox: The Sun’s rays fall directly on the equator on March 21st and September 23rd. Because neither pole is tilted towards the Sun in this unique position, the entire Earth has equal days and nights. This is referred to as an equinox. On March 21st, the Northern Hemisphere experiences spring and the Southern Hemisphere experiences autumn. While the Northern Hemisphere is experiencing autumn on September 23rd, the Southern Hemisphere is experiencing spring.

Thus, we see days,nights, and seasonal changes as a result of the Earth’s rotation and revolution around the Sun.

### 1. What are the movements of the Earth?

The Earth has two major types of motion, namely – rotation and revolution. The rotation of the Earth occurs when the Earth rotates on its axis. One rotation of the Earth on its axis takes 24 hours. This is referred to as a day. Revolution refers to the movement of the Earth around the Sun on a fixed path or orbit.

### 2. What is the daily motion of the Earth called?

The rotation of the Earth refers to its dailymotion. This occurs as the Earth rotates on its axis. One full rotation of the Earth takes about 24 hours with respect to the Sun. This causes the change between night and day on our planet, which results in one Earth day. The portion of the Earth facing the Sun experiences day, while the portion facing away from the Sun experiences night.

### 3. Why does the Southern Hemisphere experience Summer and Winter Solstice at different times than that of the Northern Hemisphere?

The Earth revolves around the Sun in a circular motion.  It is divided into two hemispheres by the Equator. Summer is experienced by the portion of the Earth facing the Sun, while winter is experienced by the portion of the Earth facing away from the Sun. As a result, the Winter and Summer Solstices occur at different times in the Southern Hemisphere than in the Northern Hemisphere.

### 4. Why do the North and South poles experience six months of day and six months of night?

As the Earth is inclined on its own axis, the Poles have six months of day and six months of night. Due to this inclination, one pole is always facing the Sun for six months and the other pole is always facing away from the Sun. That is why there are continuous days and nights at the poles for six months.

### 5. What is a leap year?

A leap year is one that has 366 days. It occurs every four years.

### 6. What is the inclination angle of the Earth’s axis with respect to its orbital plane?

The angle of inclination between the Earth’s axis and its orbital plane is 66 1/2°.