Important people

• Anaxagoras


  • Was able to explain what causes the phases of the moon
  • Explain that the moon shown only by reflected sunlight.
  • Since it is a sphere, only half is illuminated at a time. This illuminated part that is visible from the earth changes periodically
• Eudoxus


  • He proposed a system of fixed spheres
  • He believed that the sun the moon and the five known planets and the stars were attached to these spheres which carry the heavenly bodies while they revolved around the stationary earth
• Aristotle


  • The earth is spherical since it always cast a curved shadow when it eclipses the moon
  • He also believed that the earth was the center of the universe
  • The planets and stars are concentric, crystallized spheres centered on the earth
• Eratosthenes


  • The first successful attempt to determine the size of the earth was made by him
  • He did this by applying geometric principles
  • He observed the angles of the noon day sun in two egyptian cities that were almost opposite to each other ( Syene and Alexandria ) he assumed that they were in the same longitude
• Hipparcus


  • Considered as the greatest of the early greek astronomers
  • He observed and compared the brightness of 850 stars and arrange them into order of brightness or magnitude
  • She developed a method for predicting the types of lunar eclipses to within a few hours
• Claudius Ptolemy


  • He believed that the earth was the center of the universe
  • His Ptolemaic model claimed that the planets move in a complicated system of circles.
  • This geocentric model also became known as ptolemaic system