1. Astronomy
Ancient Philosophies

2. Aristotle ( ) B.C.
Greek philosopher
Believed the Earth was the center of the universe
Earth was surrounded by water, air, and fire

3. Aristotle
He thought that the moon, sun, five planets, and the stars all revolved around the Earth
Geocentric model

4. Aristarchus (3rd Century B.C)
Sun is the center of the universe
Heliocentric model
First to measure the distance to the sun and moon

5. Aristarchus
REVOLUTION is the cycle in which a planet orbits the sun (one year)
ROTATION is the cycle of a planet spinning on its axis; day to night (one day)

6. What is an axis?
Imaginary line on which an object rotates
Earth’s axis goes through its center from the North to the South Pole

7. Questions
What is the major difference between the universe models of Aristotle and Aristarchus?
How is rotation different from revolution?

8. Ptolemy (2nd century A.D)
Agreed with ARISTOTLE’S geocentric model
Retrograde motion is the idea that a planet moves back and forth in a looping motion; “Mars” (p.434)

9. Copernicus ( )
Heliocentric model
Expanded the ideas of Aristarchus
Identified the positions of the planets

10. Galileo ( )
Spent most of his life trying to prove the theories of Copernicus
First to effectively use the telescope
page 439

11. Roman Catholic Philosophy
Earth and humans are the center of all things

12. Questions
Why would the Roman Catholics care whether the Earth was the center of the universe?
What is retrograde motion?

13. Questions
What is the difference between heliocentric and geocentric?
What was Ptolemy’s theory?
Why was Galileo important?