Astronomy

Ancient Philosophies

Aristotle (384-322) B.C.

•Greek philosopher •Believed the Earth was the center of the universe

•Earth was surrounded by water, air, and fire

Aristotle

•He thought that the moon, sun, five planets, and the stars all revolved around the Earth

•Geocentric model

Aristarchus (3rd Century B.C)

•Sun is the center of the universe

•Heliocentric model•First to measure the distance to the sun and moon

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)

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

Questions

•What is the major difference between the universe models of Aristotle and Aristarchus?

•How is rotation different from revolution?

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)

Copernicus (1473-1543)

•Heliocentric model•Expanded the ideas of Aristarchus

•Identified the positions of the planets

Galileo (1564-1642)

•Spent most of his life trying to prove the theories of Copernicus

•First to effectively use the telescope

•page 439

Roman Catholic Philosophy

•Earth and humans are the center of all things

Questions

•Why would the Roman Catholics care whether the Earth was the center of the universe?

•What is retrograde motion?

Questions

•What is the difference between heliocentric and geocentric?

•What was Ptolemy’s theory?•Why was Galileo important?