Earth Introduction 

Earth is the third planet from the Sun and 75% of it is covered by water. It is the fifth largest planet with a diameter of 12,756.3 kilometers (7,973 miles) and an orbit of 149,600,000 kilometers from the Sun (93.2 million miles). From this distance, we have defined the Astronomical Unit (AU) as 1 AU to be the distance from the Sun to the Earth. The mass of Earth is measured to be 5.9736 x 10^24 kilograms.

Planet Earth travels through space at a speed of 108,000 kilometers (67,000 miles) an hour and takes 365.256 days for one orbit around the Sun. The time it takes rotate once on its axis is 23.9345 hours (commonly rounded to 24 hours).

Earth's atmosphere is made of 78% nitrogen, 21% oxygen and 1% other chemical elements. It also protects life from harmful UV radiation and burns up meteorites before they hit the surface. The molten nickel-iron core generates a magnetic field that makes compasses possible and is responsible for beautiful displays such as the auroras.

Earth is the only planet that is not named from Greek or Roman mythology, but rather from Old English and Germanic. Nonetheless, there are many other names in different languages for Earth. Such as Gaia (mother Earth) in Greek and Tellus (goddess of Earth) in Roman mythology.

Planet Earth Contents

• Introduction to Earth


• Orbital and Physical Data


• Surface
  • Plate Tectonics
    • Spreading and subduction
    • The Plates
  • Terrestrial Volcanoes
  • Calderas
  • Principal Types of Volcanoes
    • Lava Domes
    • Composite Volcanoes
    • Cinder Cones
    • Shield Volcanoes


• Atmosphere
• Chemical composition
• Greenhouse effect


• Interior
  • Layers of Earth
  • Magnetic Field
  • Solar wind and auroras
  • Van Allen radiation belts


• Exploration
• The Cradle of Life
• Seismic and diagnostic waves

• Satellites
  • The Moon
• View of Earth from the Moon
• International Space Station