Competing Cosmologies

Geocentric
Ptolemy

Heliocentric
Copernicus

Earth at center
of Solar System

Sun at center
of Solar System

Explains

• Apparent motion of Sun
• Apparent motion of Moon
• Apparent motion of Planets
• Solar and Lunar Eclipses
• Phases of Moon

Explains

• Apparent motion of Sun
• Apparent motion of Moon
• Apparent motion of Planets
• Solar and Lunar Eclipses
• Phases of Moon

Predicts

• No Parallax

• Venus & Mercury:
  • New & Crescent
    phase only

Predicts

• Parallax

• Venus & Mercury:
  • Full range of phases
    New to Full