Earth: The Only Known Life-Sustaining Planet

Formation and Structure

• Age: Approximately 4.5 billion years old.
• Formation:
  • Formed from particles after the sun's creation.
  • Gravity pulled particles together forming pebbles, boulders, and eventually Earth.
• Structure:
  • Inner Core: Solid.
  • Outer Core: Liquid.
  • Mantle: Made of flowing silicate rocks.
  • Crust: Rocky outer layer.

Position in the Solar System

• Third planet from the Sun.
• Distance: Average of 93 million miles from the Sun.
• Conditions:
  • Close enough to be warm but not overly hot.
  • Conditions prevent extreme heat and solar radiation like Mercury.

Unique Features

• Liquid Water:
  • Earth maintains liquid surface water, unlike any other known planet.
  • Water exists in all forms: liquid, ice, gas.
  • Contributes to nutrient-rich soil and forms oceans and freshwater systems.
  • Cycles moisture into Earth's atmosphere.

Origin of Life

• Primitive Life:
  • Began approximately 3.8 billion years ago.
  • Started in Earth's oceans with microbial organisms.
• Biodiversity:
  • Earth's life forms have evolved into a vast array of species.
  • Estimated 1.5 million species documented.
  • Potential for millions more undiscovered species.

Earth's Ecosystem

• Ecosystem:
  • Global ecosystem fueled by water.
  • Houses a diverse range of life forms.
  • Curiosity and grandness paralleled by astronomical events enabling its formation.

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These notes summarize the key points from a lecture on Earth's formation, structure, unique positioning, and the evolution of life on the planet.