Science

• One of the factors that make our planet habitable is its atmosphere
• Atmosphere


  The blanket or envelope of gases surrounding the earth
• The atmosphere keeps us warm, gives us oxygen to breathe, and is where weather happens
• The atmosphere keeps the overall temperature of the earth fairly steady, especially between night and day
• Gases in the earth's atmosphere


  • 78% nitrogen
  • 21% oxygen
  • 1% other trace gases including carbon dioxide, inert gases, hydrogen, methane, ozone
• Layers of the atmosphere from ground level upward


  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • Exosphere
• Basis for dividing the atmosphere into layers

  Change of temperature with height
• Troposphere


  • Lowest layer
  • Makes up 75% of total mass of atmosphere
  • Contains 99% of atmosphere's water
  • Where wind, clouds, and weather phenomena take place
  • Air is constantly moving
• Stratosphere


  • Air flow is more stable than troposphere
  • Ozone layer is found here
  • Protects from harmful UV radiation
• Mesosphere


  • Temperature decreases with height
  • Coldest layer
  • Burns up most meteors and asteroids before reaching Earth's surface
• Thermosphere


  • Closer to the sun
  • Absorbs a large amount of solar radiation
  • Temperature increases tremendously
  • International Space Station and space shuttles orbit in this layer
  • Ionosphere is found within this layer
• Exosphere


  • Merges into outer space
  • Temperature varies from very hot to very cold
  • Ideal for placing artificial satellites as there is little friction
• Auroras are bands of light with different colors, called aurora borealis in the north and aurora australis in the south