ancient astronomy

• Plato believed that the universe is perfect or ethereal and unchanging.
• According to Eudoxus of Cnidus, there are 27 interconnected geocentric spheres.
• Plato


  he further described the stars embedded in outer space as eternal and divine.
• aristotle 


  in conjunction to Eudoxus model he added 3 spheres to jupiter and mars; 4 spheres to sun, moon, venus and mercury.
• Claudius Ptolemny

  1. earth is a spherical object
  2. the stars are fixed bodies attached to a solid spherical exterior part of the universe
  3. planets move independently of the fixed stars, and sometimes, the planets seem to reverse their motion.
• Aristarchus of Samos

  1. he stated that the sun and stars are fixed.
  2. estimated the sizes of the sun and moon as compared to Earth's size
  3. estimated the distances from the earth to the sun and moon (sun is about 18-20x farther away from earth than moon)
• moon's diameter

  0.32-0.40x
• sun's diameter 


  6.3-7.2x