EARTH (OUR PLANET)

PRERNA FOR IAS

EARTH (OUR PLANET)

1. Earth (Our Planet)

Earth is the third planet from the Sun and the only known planet that supports life. It has a geoid shape, meaning it is slightly flattened at the poles and bulged at the equator. Earth is about 4.54 billion years old and revolves around the Sun while rotating on its axis. Its atmosphere, water, and suitable temperature make life possible. About 71% of Earth’s surface is covered by water and 29% by land. The planet has one natural satellite, the Moon. Earth’s unique combination of air, water, land, and living organisms forms a dynamic and interconnected environment.

2. Key Facts About Earth

Earth has several important physical characteristics. It is the third planet from the Sun and has a diameter of approximately 12,756 km. Its circumference is about 40,075 km, and its average density is 5.52 g/cm³. Earth rotates once every 23 hours 56 minutes 4 seconds and completes one revolution around the Sun in about 365 days. It is located nearly 149.6 million km from the Sun. The escape velocity of Earth is 11.2 km/s. Earth’s axis is tilted at 23.5°, which causes seasonal changes. These facts help scientists understand Earth’s structure and behavior.

3. Atmosphere (Composition)

The atmosphere is the layer of gases surrounding Earth that supports life and protects living organisms. It is mainly composed of Nitrogen (78%) and Oxygen (21%), while the remaining 1% consists of gases such as Argon, Carbon Dioxide, Neon, and others. Oxygen is essential for respiration, while nitrogen helps maintain ecological balance. The atmosphere regulates temperature, protects Earth from harmful solar radiation, and supports weather and climate systems. Without the atmosphere, life would not be possible. It also acts as a shield against meteoroids, preventing many of them from reaching Earth’s surface.

4. Earth Records

Earth has several remarkable geographical records. Mount Everest, located in the Himalayas, is the highest point on Earth, standing at about 8,849 meters above sea level. The Mariana Trench in the Pacific Ocean contains the Challenger Deep, the deepest known point on Earth. The average global temperature is around 15°C, creating conditions suitable for life. Earth’s average humidity ranges between 30% and 35%. These records help scientists understand the planet’s physical extremes and environmental conditions. They also provide valuable information for geographical studies, climate research, and exploration activities around the world.

5. Internal Structure of Earth

The Earth is divided into three main layers: the crust, mantle, and core. The crust is the outermost solid layer where humans live. Beneath it lies the mantle, a semi-solid layer composed of hot rocks and minerals. The innermost part is the core, which consists of a liquid outer core and a solid inner core mainly made of iron and nickel. These layers differ in temperature, density, and composition. The movement of materials within the mantle causes tectonic activities such as earthquakes and volcanic eruptions. Understanding Earth’s internal structure helps explain many geological processes.

6. Major Movements of Earth

Earth performs two major movements: rotation and revolution. Rotation is the spinning of Earth on its axis, causing day and night. Revolution is Earth’s movement around the Sun, resulting in the changing seasons. During its orbit, Earth reaches Perihelion (closest to the Sun) around January 3 and Aphelion (farthest from the Sun) around July 4. Equinoxes occur around March 21 and September 23 when day and night are equal. Solstices occur on June 21 and December 22, marking the longest day and longest night respectively. These movements influence climate, seasons, and weather patterns globally.

7. Important Lines of Latitude

Important latitudinal lines divide Earth into climatic zones. The Equator (0°) divides Earth into Northern and Southern Hemispheres. The Tropic of Cancer (23½° N) and Tropic of Capricorn (23½° S) mark the limits of the tropical zone. The Arctic Circle (66½° N) and Antarctic Circle (66½° S) define the polar regions. These imaginary lines are essential for understanding climate, temperature distribution, and sunlight patterns across the globe. They help geographers study seasonal changes and the varying lengths of days and nights experienced in different parts of the world.

8. Rotation of Earth

Rotation refers to Earth spinning on its own axis from west to east. One complete rotation takes approximately 23 hours 56 minutes and 4 seconds. This movement causes the occurrence of day and night. As Earth rotates, different parts face the Sun at different times, creating daylight and darkness. Rotation also influences wind patterns, ocean currents, and the Coriolis effect, which affects weather systems. The speed of rotation is highest at the Equator and decreases toward the poles. This continuous movement is essential for maintaining Earth’s environmental balance and regulating daily temperature variations.

9. Revolution of Earth

Revolution is the movement of Earth around the Sun in an elliptical orbit. One complete revolution takes approximately 365 days, 5 hours, 48 minutes, and 46 seconds. Along with Earth’s axial tilt of 23.5°, revolution causes the changing seasons. During different parts of the orbit, various regions receive different amounts of sunlight, resulting in summer, winter, spring, and autumn. Revolution also determines the length of a year and influences climatic conditions globally. Leap years are introduced every four years to account for the extra hours accumulated during Earth’s revolution around the Sun.

10. Earth’s Age, Density, and Gravity

Earth is estimated to be about 4.54 billion years old based on scientific studies of rocks and meteorites. Its average density is approximately 5.52 g/cm³, making it the densest planet in the Solar System. Gravity on Earth is about 9.8 m/s² and is responsible for keeping objects, water, and the atmosphere bound to the planet. Gravity allows life to exist by maintaining stable environmental conditions. Earth’s age helps scientists understand geological evolution, while density and gravity provide insights into its internal composition and physical properties. These factors are fundamental to Earth science and planetary studies.