NCERT Notes: Grade 6 Social Science - Geography - Chapter 3: Motions of the Earth

Introduction

The Earth, our home planet, isn’t static. It’s continually on the move. Chapter 3 of the NCERT Grade 6 Social Science textbook introduces students to the major motions of the Earth and their consequences.

Earth’s Movements: An Overview

The Earth primarily has two main types of motions:

1. Rotation: The spinning of Earth around its imaginary axis.
2. Revolution: Earth’s orbiting journey around the Sun.

1. Rotation of the Earth

What is it?

• Rotation refers to the Earth spinning on its imaginary axis. This axis runs from the North Pole to the South Pole.

Duration:

• The Earth takes approximately 24 hours to complete one rotation.

Effects of Rotation:

1. Day and Night: As Earth rotates, different parts of the planet face the Sun, resulting in day, while the areas facing away experience night.

2. Variation in the Length of Days and Nights: Due to the axial tilt and Earth’s curved shape, the length of days and nights varies, especially when moving away from the equator.

2. Revolution of the Earth

What is it?

• Revolution is the elliptical orbiting of Earth around the Sun.

Duration:

• The Earth completes its revolution in about 365¼ days. This period is what we call a year. To account for the extra one-fourth day, we have a leap year every four years with an additional day in February.

Effects of Revolution:

1. Seasons: The primary consequence of Earth’s revolution is the change in seasons. This change is also affected by the tilt of Earth’s axis, which is approximately 23.5 degrees.

2. Variation in the Duration of Days and Nights: As the Earth orbits the Sun, the Northern and Southern Hemispheres receive varying amounts of sunlight, leading to differences in day lengths.

3. Solstices and Equinoxes: These are significant events caused by Earth’s revolution and axial tilt.

   • Summer Solstice: Around June 21, when the Northern Hemisphere experiences the longest day and the shortest night.

   • Winter Solstice: Around December 22, when the Northern Hemisphere has the shortest day and the longest night.

   • Equinoxes: Days when day and night are almost equal. This occurs twice a year: around March 21 (Vernal Equinox) and September 23 (Autumnal Equinox).

Understanding Earth’s Tilt

The Earth’s axis isn’t upright. It’s tilted at an angle of 23.5 degrees. This tilt, combined with the revolution, causes varying intensities and durations of sunlight in different regions, leading to seasons.

Conclusion

The motions of the Earth play a crucial role in our daily lives, influencing the length of our days and nights, and even the changing of seasons. These cyclic movements, rotation, and revolution shape our understanding of time, the concept of a day, and a year. By comprehending these motions, we not only appreciate the cosmic dance our planet is engaged in but also the rhythmic patterns of nature that have been a constant through ages.

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Reference: NCERT Grade 6 Social Science - Geography - Chapter 3: Motions of the Earth