1. A Brief History of Astronomy 350 bce. - mid 1600’s ce.

2. Aristotle's Theory : 350 bce Geocentric model of the Earth –Earth is the center of the universe –Earth does not move –Everything circles the earth

3. The Problem Retrograde Motion –Or Wandering Planets Mars and Venus appear from earth to move backwards in their orbit

4. Ptolemy’s Solution 140ce 490 years later Based on 80 perfect circles Large circles - Deferents Small circles - Epicycles BUT: Very complex - Could call it messy

5. 13 centuries later: 1543 ce Copernicus: Heliocentric model Earth is not the center of everything Earth only center of moon’s orbit All planets revolve around the sun Universe is unbelievably large Any motion seen in the stars is result of earth’s motion Sun does not move – its motion is a result of earths movement Retrograde motion can be explained by earth’s motion

6. No One Listened! Why? Published after Copernicus’ Death No Mathematical model to back it up Published in Latin: Which was not widely read It went against: –Tradition –The Catholic Church (cultural power) –Common sense

7. 1608 ce: Birth of Modern Astronomy Galileo –Use Telescope to look into space –Discovered: mountains, valleys, and craters on the Moon That the Sun rotates once a month (Sun Spots) Four moons of Jupiter Phases of Venus –Brought focus back to Heliocentric model

8. Galileo’s Trials Heliocentric model still went against: –Tradition –The Catholic Church (cultural Power) –Common sense Forced to retract theory by Catholic Church* Goes blind from looking at the sun Dies under house arrest Feud with Tycho Brahe –Collecting data to support Geocentric model during the same time –Working for the Catholic Church

9. Sweet Irony (just a few years after Galileo) Brahe’s assistant: Kepler –Feared by Brahe –Assigned to Mars –Uses Mars's Retrograde motion to build a mathematic model supporting Galileo –Published in 1621 ce More on Kepler later Newton’s laws of motion –mid 1600’s –explained the motion outlined by his predecessors

10. To Sum Up Aristotle 350 bce Ptolemy 140ce 1543 ce Copernicus Galileo 1608 ce Kepler 1621 ce Newton’s laws of motion 1685 ce Brahe Adopted by the C.C. 1616ce Geocentric Heliocentric