Earth: Our Home and Life

Earth: Our Home

• The solar system is a group of planets that orbit the sun.
• Earth is the third planet from the sun.
• The order of the inner planets from the closest to the farthest from the sun is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune (Mnemonic: My Very Excited Mother Just Served Us Noodles).
• Scientists look for evidence of water, oxygen/methane-rich atmospheres, and a planet's ideal distance from its sun for potential life.

Why is Life Possible on Earth?

• Earth's ideal distance from the sun maintains a temperature range suitable for life (neither too hot nor too cold).
• Its magnetic field protects it from harmful solar radiation.
• A protective atmosphere traps heat and maintains suitable temperatures.
• Earth has the essential chemical elements for life, including carbon and water.

Earth's Shape and Rotation

• Earth is close to a sphere, but not perfectly spherical.
• Its rotation causes a bulge at the equator and a flattening at the poles, creating an oblate ellipsoid shape.
• Earth rotates on its axis (an imaginary line through its center) tilted at 23.5 degrees.
• The poles are where the axis crosses the Earth's surface.
• One complete rotation defines a solar day, lasting 24 hours.

Earth's Rotation and Day/Night Cycle

• Earth's rotation is the spinning motion from west to east on its axis.
• During rotation, only one side of the Earth faces the sun, experiencing day.
• The other side faces away from the sun, experiencing night.
• The apparent movement of the sun across the sky is due to Earth’s rotation, not the sun's movement itself.

Earth's Revolution and Seasons

• Earth revolves around the sun in an elliptical orbit, taking 365 ¼ days.
• The Earth's tilted axis (23.5 degrees) causes different parts of Earth to receive varying amounts of sunlight throughout the year.
• This results in the changing seasons.
• In December, the northern hemisphere is tilted away from the sun, experiencing winter, while the southern hemisphere is tilted towards the sun, experiencing summer.
• The opposite happens in June.

The Fragile Earth and Sustainable Development

• Earth's resources are finite and need to be used carefully to sustain life and support future generations.
• Rapid resource consumption can deplete resources faster than they can regenerate.
• Activities like deforestation and vehicle emissions affect the environment.
• Sustainable development is crucial to meet the needs of the present without impacting future generations.