ASTRONOMERS

ARISTOLE

• He thought Earth was at the center of all thing.
• His model had Earth that the center of the solar system.
• He thought that if Earth went around the sun then the position of the stars would change.

ARISTARCHUS

• Reported to have had a heliocentric model of the solar system.
• His model wasn't widely accepted at his time.
• Attempted to measure the distances to the moon and sun.
• Although his ratio was to small it was very important to science

PTOLEMY

• Ptolemy has a book that has planet observations from 800 years ago.
• Developed a detailed geocentric model that was used for next 14 centuries.
• Believed that a celestial body traveled constant speed in perfect circle.
• The planets moved in small circles then moved on larger circles.
• This system fits observations better than any before.

CORPERNICUS

• Felt Ptolemy's model too complicated.
• Aware of heliocentric idea Aristarchus.
• Copernicus observation done by eye.
• Adopted Ptolemy idea planets travel circles.
• Developed heliocentric model.

KEPLER

• Found that ellipses best fit planet path.
• Created Kepler's Laws
• 1st law planet orbits are ellipses sun at center.
• 2nd law planets faster when orbit closer to sun.
• 3rd law relates distance planet from sun to time takes one orbit.

GALILEO

• Made significant improvements to newly invented telescope.
• Used more powerful telescope view celestial objects.
• Observed moons Io, Europa, Callisto, and Ganymede.
• Observations show Earth not only object being orbited.
• Gave support to heliocentric model.