Notes on Earth's Atmosphere

Earth's Atmosphere Overview

• Definition: Earth's atmosphere is a protective layer of gases surrounding the planet, essential for life.
• Composition:
  • 78% nitrogen
  • 21% oxygen
  • 1% other gases (argon, carbon dioxide, etc.)

Importance of the Atmosphere

• Regulates solar energy, affecting climate and weather, and provides breathable oxygen.
• Shields Earth from harmful UV radiation.
• Maintains temperatures suitable for life through the greenhouse effect.

Layers of the Atmosphere

1. Troposphere:

   • Closest layer to Earth.
   • Contains 75% of atmospheric gases.
   • Weather occurs here, with highest density and greatest air pressure.

2. Stratosphere:

   • Contains the ozone layer which absorbs UV radiation.
   • Less turbulent, allowing planes to fly here.

3. Mesosphere:

   • Coldest layer (up to -90°C).
   • Burns most meteoroids due to thin air friction.

4. Thermosphere:

   • Largest layer, absorbs solar radiation.
   • High temperatures but thin air prevents heat sensation.
   • Home to the ionosphere, crucial for radio communications and the auroras.

5. Exosphere:

   • Outermost layer, extending from about 700 km to 10,000 km.
   • No clear boundary with outer space.

Atmospheric Phenomena

• Auroras: Display of lights in polar regions caused by solar particles colliding with atmospheric gases.
• Temperature Gradients: Temperature changes with altitude; generally decreases in the troposphere and increases in the thermosphere.

Summary

• Earth's atmosphere is vital for sustaining life, influencing weather, and regulating temperatures.
• Each layer of the atmosphere has distinct characteristics that support different atmospheric phenomena and functions critical for life on Earth.