1. Page 588- Solar System Models
GEOCENTRIC Models HELIOCENTRIC Models
Ancient Greeks Europeans
300 B.C.
1400’s
Aristotle Ptolemy Copernicus Galileo Newton
Tycho Kepler
Brahe

3. Sun Moon Stars (Milky Way arm)
As viewed from Earth in Greece 2000 years ago
Sun
Moon
Stars
(Milky Way arm)

4. Aristotle (350 B.C.) Greek
Formulated a picture of the solar system that put Earth at its center with all the other heavenly bodies orbiting around it.
GEOCENTRIC model
The orbits were perfect circles.

5. Sun
Moon
stars

6. The “Wanderers” The Greeks continued to watch the night sky,
The Sun, moon, stars moved in a predictable orbit in the sky.
BUT, there were five “objects” that did not follow this regular, predictable motion
Once every year, they’d move BACKWARDS (retrograde) for a month or two!!
They “wandered”, thus called planetes
(Mercury, Venus, Mars, Jupiter, Saturn)

7. The retrograde (backward, looping) motion of Mars.
A composite image created by superimposing images taken on twenty-nine different dates.
The planets: Mars. Venus etc. moved in a looping motion relative to Earth.

8. Observations http://www.davidcolarusso.com/astro/
Watch the animation and make observations about the motions of the planets and the Sun. Write these observations by the correct symbol for the planet on your paper (opposite side of the POM chart)
Draw a BIRD’S-EYE-VIEW (as if you were looking down at it) of all the planets and the sun as they appeared in the animation. REMEMBER you are drawing this as if you existed in Ancient Greece and before technology told us what we know about the planets and their positions and motion.
Slow the motion as close to 0 zero as you can. Change the View and check one planet at a time to see its motion separately.

9. Sun,
Planets:
Mercury
Venus
Mars
Jupiter
Saturn

10. Whiteboard Time
Discuss your diagram with your partner and draw a diagram of a mutual BIRD’S-EYE-VIEW that both of you can agree upon. Place it standing up on a lab table when you are done.

11. What does this look like?
Ptolemy (Greek) A.D. 140
He attempted to construct a model of the solar system that explained the motions of the planets.
The model had to be testable by predicting future motion
What does this look like?

12. Ptolemy’s model of the Solar System/Universe
Epicycle

13. To be continued….
His model explained the observed motion of the planets.
His model enabled them to predict the future motion of planets.
But it was way too complicated!
And it was not right.
History Channel (4 min)
Ptolemy (3 min.)

14. Historical explanations**
Measurements
**But Wrong!!

15. Page 588- Solar System Models
GEOCENTRIC Models HELIOCENTRIC Models
Ancient Greeks Europeans
300 B.C.-140 A.D.
1400’s
Aristotle Ptolemy Copernicus / Galileo Newton
Tycho Kepler
Brahe