• "Earth writing" or "Earth description"
  
  
• Physical, Cultural, Regional, Technical
  
  
• Environmental spheres: Lithosphere, Atmosphere, Hydrosphere, Biosphere
  
  

Earth and the Sun

From just the moons vantage — Earth is a tiny Christmas tree ornament

Size and Shape of Earth

• 24,900 miles circumference; nearly 7,926 mi. diameter
• Spheroid or Ellipsoid — not a perfect sphere
  • Forces of Earth’s rotation, bulges at center
    • Slight! (only 27 mi difference), yet affects maps, navigation and aeronautics
    • Also topography or landforms
      • Mt. Everest and Mariana Trench (36,000 feet below sea level!)

Globes and Great Circles

• globes - best model to represent the Earth (no distortion, seasons, distance)
  
  
• Great Circle - largest circle around Earth
  • Shortest distance between two locations on Earth
  • Divides the Earth exactly in half

Latitude and Longitude (geographic grid system)

• How would you describe a location on a ball?
  • Greeks - localized grid system for round world!
    
    
• latitude - also known as "Parallels"
• angle from center to poles (fixed unlike ball)
  • Greeks used crude sextant and stars (300 B.C.)
• one degree divided into minutes and seconds only
• about 69 miles per 1 degree
  
  
• longitude - also known as "Meridians"
• historically difficult to measure rate without time piece (watch) and reference point
• measured knots on a rope to calculate rate away from land
  • 1759 - the first timepiece able to keep time at sea!
  • 1884 - establish universal starting point for longitude
    • Greenwich, England

Longitude and Time

• Local time based on solar noon
  
  
• Development of transportation and communication
  • Today we have 24 time zones
    • 360 degrees / 24 hours = 15 degrees for time zone
      
      
• International Date Line
• Opposite side of Prime Meridian to lapse into next day
  
  
• world-wide reference of Greenwich Mean Time (GMT)
  • now written as Coordinated Univeral Time (UTC) or Zulu Time