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From keywordswiki

A composite image of the Western hemisphere of the Earth
  • Earth is the third planet from the Sun, and the only astronomical object known to harbor life.
  • According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago.[1]
  • Earth's gravity interacts with other objects in space, especially the Sun and the Moon, Earth's only natural satellite. Earth orbits around the Sun in 365.26 days, a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times
  • Earth's axis of rotation is tilted with respect to its orbital plane, producing seasons on Earth.
  • The gravitational interaction between Earth and the Moon causes tides, stabilizes Earth's orientation on its axis, and gradually slows its rotation.
  • Earth is the densest planet in the Solar System and the largest and most massive of the four terrestrial planets.
  • Within the first billion years of Earth's history, life appeared in the oceans and began to affect the Earth's atmosphere and surface, leading to the proliferation of aerobic and anaerobic organisms.
  • Some geological evidence indicates that life may have arisen as early as 4.1 billion years ago.
  • Over 7.7 billion humans live on Earth and depend on its biosphere and natural resources for their survival.[3] Humans have developed diverse societies and cultures; politically, the world has about 200 sovereign states.