Earth As a Planet

• The earth is the 3rd planet from the sun and the 5th largest in the solar system
• from space, the earth looks blue as 70% of its total area is covered by water
• The earth is also called the watery planet
• the family of the sun is called the solar system
• the chief members of the solar system are the planets, the satellites that revolve around the planets and other celestial bodies such as asteroids, comets and meteorites
• The planets in order from the sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
• The earth is not a perfect sphere. It bulges slightly at the centre and is flattened at the poles
• To conduct the Bedford Level Experiment, 3 poles of equal length were placed at an interval of 5 kms
• The pole star can be seen at an angle of 90 degrees at the north pole
• At the equator, the angle of the pole star is 0 degrees
• Jean Baptiste Delambre discovered the flattening of the earth at the poles
• Best proof that the earth is spherical in shape: Satellite Pictures
• In modern days, all radio waves that travel across the earth can only be heard within a certain horizon. this is due to the spherical shape of the earth
• the sun rises in the east and sets in the west
• the earth rotates from west to east
• people in the east can see the sun earlier than people in the west
• the earths diameter at the equator is 12756km and diameter at the poles is 12714km
• difference in diameter is due to the centrifugal force
• centrifugal force is a force that causes an object moving in a circular path to move out and away from the centre of its path (taking a curve)
• the shape of the earth is an oblate spheroid
• the earth has an average temperature of 17 degrees celsius
• nitrogen: 78%, oxygen: 21%, other gases: less than 1%
• distribution of water is responsible for moderating the climate and surface condition of the earth
• The self- regulating and self-sustaining structural and functional unit of the biosphere is called the ecosystem
• The vast network of all interconnected ecosystems constitute the biosphere.
• The biosphere is the life zone of the earth