Heliocentric Model

• Came around the 1500s thanks to Copernicus
  • He realized many of the observed motions in the sky could be explained by the Earth moving around the Sun while rotating
    • The motion of the Sun
    • The rotation of the celestial sphere (the Earth rotates, not the sphere)
• Explains retrograde motion by placing the Sun at the center
• Less clumsy and has better symmetry than Ptolemy's model (geocentric model)

Space Astronomy Planetary Motion