Movement of Earth

• Rotation
  • turns on axis every 24 hours (planet comparisons)
    • apparent sunrise from Earth's rotation
    • Circle of illumination — Great Circle divides the light
      
      
• Revolution
  • Around sun
  • Not pefect circle either, but elliptical orbit
    • closer during winter and farther in summer
      • Jan 3^rd closest - perihelion
      • July 4^th farther- aphelion
    • Completes revolution in about 365 1/4 day
      (leap year every 4 years)
      
      

Other important factors

• Plane of the Ecliptic - Plane directly around sun
  
  
• Inclination — Earth tilts 23 1/2 degrees from the perpendicular plane
  
  
• Parallelism — always points in one direction as it revolves around the sun
  • affects solar intensit