ASTRONOMERS IN HISTORY

ARISTOTLE

• Postulated a fifth element called aether, which he believed to be the main constituent of the celestial bodies
• Aristotle's view of the universe was hierarchical, and he made a sharp distinction between the sublunar world of change, and the eternal and immutable heavens

ARISTARCHUS

• Aristarchus of Samos, Greek astronomer who maintained that Earth rotates on its axis and revolves around the Sun
• He had introduced the fact that the Earth rotates on its axis and revolves around the sun to the world.

PTOLEMY

• Astronomer, geographer, and mathematician
• Developed a detailed geocentric model that was used by astronomers for the next 14 centuries

COPERNICUS

• The polish astronomer felt that the Ptolemy's model of the solar system was too complicated
• Planetary paths should be perfect circles

KEPLER

• German mathematician and astronomer
• He realized that requiring planetary motions to be exactly circular did not fit the observations perfectly.

GALILEO GALILEI

• A scientist who approached questions in the fashion that today we call scientific methods.
• He observed the moons, Io, Europa, Callisto, and Ganymede orbiting Jupiter.