the earth

• The Earth


  The third planet from the Sun and the only planet to have an atmosphere with oxygen and water
• The Earth is neither too far nor too close to the Sun
• This creates favourable conditions to support life on the Earth
• Shape of the Earth

  • Appears round like any other planets
  • Slightly bulged at the equator and flattened at the poles due to gravity and variation in the speed of rotation
  • Oblate spheroid
• Distortion of the Earth's sphere

  1. Rotation causes centrifugal force

  2. Centrifugal force is greatest at the equator causing the slightly outward bulge

  3. Circumference and diameter of the Earth is larger at the equator than at the poles
• Proofs to show that the Earth is not flat

  • Varying time of Sunrise
  • Ship and the horizon
  • Bedford level experiment
• Bedford level experiment shows the curvature of the Earth
• A spherical object will always cast a circular shadow
• Types of lunar eclipses

  • Total
  • Partial
  • Penumbral
• The Sun, Moon and all the celestial bodies appear to be spherical from different positions
• Photographs of the Earth taken from space prove beyond doubt that the Earth is a sphere
• Size of the Earth

  • Fifth largest planet in the solar system
  • Smaller than the four gas giants but larger than the three rocky planets
  • Circumference of about 40,075 km at the equator and 40,008 km at the poles
  • Densest planet due to metallic core and rocky mantle, and crust
  • Average radius of 6371 km
  • Smaller than Mercury by 38%
• The Earth is a unique planet as it supports life
• Life on Earth

  • About 1,000,000 species of animals
  • More than 350,000 species of plants
• The Earth is about 150 million kilometres away from the Sun with an average surface temperature of 140 C making it neither too hot nor too cold
• The Earth is the only planet in the solar system that has water in liquid form covering about 71% of its surface
• The heat capacity of the ocean is important to maintain the Earth's temperature relatively stable
• The occurrence of the water cycle on the Earth makes water available continuously