1. Study Points
Describe the geocentric and the heliocentric models of the solar system.
The word planet derives from the Greek "planetes" which means wanderer. Why were the planets called wanderers?
Explain Aristotle’s main argument against the heliocentric model.
What was Aristotle’s other (and weaker) argument against the heliocentric model?
Who gave the first evidence in favor of the heliocentric model? What was the evidence?
Who added the mathematical calculations to the geocentric model?
When a planet undergoes retrograde motion, how does it look?
How did the geocentric model explain retrograde motion?
How did the heliocentric model explain retrograde motion?
For 2 lectures on Copernican Revolution
**Schedule 5&5 for fall 2017**

2. Before the Copernican Revolution
Part 1 of 2 Lectures on the Copernican Revolution

3. Before the Copernican Revolution – Greek Astronomy
Western only – Please investigate other cultures
Greeks (influenced by Babylonia, Mesopotamia, Egypt, Rome)
~700 BC to ~140 AD
Some ideas and people
Know the starred* items
Demos: Software for sky, Geocentric model, Heliocentric model, Earth globe

4. Everything orbits around…
Earth
Sun
Heliocentric Model*
- Sun-centered
(from Copernicus, AD)
Geocentric Model*
- Earth-centered
(from Aristotle, BC)

5. Prior to the Copernican Revolution – Greek Astronomy
~700 BC Astronomy
Early astronomy was about time keeping (when to sow/plant and reap/harvest crops)
Prior to the Copernican Revolution – Greek Astronomy

6. Prior to the Copernican Revolution – Greek Astronomy
Hesiod, Works and Days, ~700 BC
... when the Pleiades rise it is time to use the sickle, but the plough when they are setting; 40 days they stay away from heaven; when Arcturus ascends from the sea and, rising in the evening, remain visible for the entire night, the grapes must be pruned;…
Needed better observations to keep the various planting calendars synchronized.
Hesiod, Greek poet
Islamic and Arabic astronomy centered around time and understanding when to pray
Prior to the Copernican Revolution – Greek Astronomy

7. Prior to the Copernican Revolution – Greek Astronomy
Greeks ~500 BC
What is the sun? Fire?
Tiny lights in the sky?
Why do 7 lights wander among the others?
7 Planetes* = wanderers*
The 7 included: Sun, Moon, Mercury, Venus, Mars, Jupiter & Saturn
Planete means wanderer
science.msfc.nasa.gov/ ssl/pad/solar/surface.htm
imagine.gsfc.nasa.gov/.../ news/22apr02.html
Prior to the Copernican Revolution – Greek Astronomy

8. Prior to the Copernican Revolution – Greek Astronomy
Pythagoras of Samos ~500 BC
Earth is a sphere
Sphere is perfection in math
Crystal spheres for 7 planetes: Sun, Moon, 5 planets
Already thinking geocentric
Pythagoras’ Theorum a^2+b^2=c^2 for right triangles
Prior to the Copernican Revolution – Greek Astronomy

9. Prior to the Copernican Revolution – Greek Astronomy
Plato ~360 BC
Heavens are perfect, unchanging (from mathematical perfection)
Heavenly motion must be in circles and uniform
Remember science starts with the simplest idea first: circles are less complex than ovals or other shapes
Prior to the Copernican Revolution – Greek Astronomy

10. Prior to the Copernican Revolution – Greek Astronomy
Aristotle ~350 BC
Plato’s student
Earth: corrupt, changeable, imperfect
Separation of perfect heavens and Earth
Arguments for geocentric model*
No parallax of stars** (strongest argument)
Should see parallax with heliocentric (we do now)
Moon would be left behind if Sun-centered*
Parallax is the apparent change in position of an object due to the change in position of the object or the observer
Parallax thumb demonstration
If Earth wasn’t the center then we would leave the Moon behind.
He didn’t see any parallax of stars so we are the center. The truth is that there is parallax of the stars but it is so little because they are so far away that we don’t see the parallax with the naked or unaided eye.
Prior to the Copernican Revolution – Greek Astronomy

11. Prior to the Copernican Revolution – Greek Astronomy
Aristarchus ~300 BC
Heliocentric solar system (first evidence)*
Measured size of Sun*
Measured Sun was much further away than Moon
Prior to the Copernican Revolution – Greek Astronomy

12. Prior to the Copernican Revolution – Greek Astronomy
Ptolemy ~140 AD
Geocentric model* (often called the Ptolemaic system)
Mathematical model of universe*
Perfect Bodies and orbits
circles, spheres
Uniform motion
Epicycles explain retrograde motion*
Prior to the Copernican Revolution – Greek Astronomy

13. From Cycles of the Sky & Moon Lectures
Already know this:
Minute to Minute: the Sun, Moon, stars, planets appear to rise in East and set in West due to Earth’s spin (rotation). (East to West)
Day to Day: Moon moves West to East due to Moon’s orbit (revolution) around Earth.
New information:
Day to Day: Planets typically move West to East due to their orbits around the Sun.
Retrograde Day to Day Motion: Planets move East to West due to their orbits around the Sun and the difference in speeds of Earth and other planet.

14. Retrograde Motion (Day to Day)
Sometimes planets moved backwards against the background of stars.
All other planets have retrograde motion in our sky: inner planets and outer planets
Retrograde motion is East to West and observed day to day.
Minute to minute motion across sky is still East to West due to Earth’s rotation.

15. Ptolemy Geocentric Model Perfect circles, spheres, uniform motion
Mars’ Epicycle
Earth
Mars

16. Copernican Revolution
Both models explain observations…
Retrograde motion of planets
Copernican Revolution

17. Copernican Revolution
Retrograde motion – Geocentric Explanation
Planets ride on epicycles
Sometimes appear to
move backwards
Copernican Revolution

18. Copernican Revolution
Retrograde motion – Heliocentric Explanation
One planet overtakes
another planet.
Slower planet appears to
move backwards.
Copernican Revolution

19. Copernican Revolution
Retrograde motion – Heliocentric
New (and correct) explanation of retrograde motion of the planets.
Retrograde (westward) motion of a planet occurs when the Earth passes the planet.
Ptolemy’s epicylces unnecessary
Copernican Revolution

20. Prior to the Copernican Revolution – Greek Astronomy
Dark Ages in Europe
5th to 15th centuries AD: AD
Roman libraries sacked
Often violent mix of Latin and Arabic cultures
Plague, famine, wars
Islamic Golden Age of Science (8th to 13th centuries)
Long time between Ptolemy ~140 AD to Copernicus ~1500 AD.
Black Death/Bubonic Plague killed about 50 million people in 14th century (1300’s) in Europe, Asia & Africa
Famine in Europe in 1300’s
Wars: Roman Empire conquering, then to Byzantine Empire
Ptolemy 140AD
Prior to the Copernican Revolution – Greek Astronomy

21. Summary Before Copernicus ~700BC to 140 AD Geocentric Model Dominated
Pythagoras of Samos
Plato
Aristotle*
Aristarchus*
Ptolemy*

22. Observation Projects
OBSERVATION PROJECTS: (in order of due date) 115+ points as options. Maximum cannot exceed 100 points.
X Earth-Sun Scale Model Due Sep. 5 (10 points)
JUST ADDED: Student Success Day Due. Sep. 14 (occurs on Sep. 13) (5 points) Go to an event on 9/13
Sunset – Part 1 Due Sep. 21 (5 points) Take a picture of the sunset
JUST ADDED: Astrophysics Lecture Due Sep. 27 (10 points) Attend
Moon Phases Due Oct. 12 (10 points) Record 4 phases & table info
Sunset – Part 2 Due Nov. 30 (5 points) Take 2nd picture of sunset
Planetarium (Plan) Due Dec. 12 (10 points) Go to a planetarium
Star Gazing (SG) Due Dec. 12 (25 points) Expert shows stars+more
Telescope (Tel) Due Dec. 12 (25 points) Look through telescope
Moon Craters (MC) Due Dec. 12 (10 points) Look at moon craters through a telescope or binoculars
Point out Student Success Day and look for website. Work on Sunset and Moon Phases – more info next slide
Go through Sunset Part 1 – didn’t cover that Tuesday! More info on next slide too.

23. Observation Projects
Student Success Day, Due Sep. 14; Complete Sep. 13 (5 obs. points)
Planetarium: Exploradome at MCTC on Wed, Sep. 13 (10 obs. points)
8:30am to 2pm in the Gym of the Bowman Building, lower level
Shows every 30 min
Sign-in sheet for credit
Sunset Part 1, Due Sep. 21 (5 obs. points)
Sunset times:
Phone App: Sunrise Sunset or Weather App
Astrophysics Lecture at Univ. of Minnesota, Due Sep. 27 (10 obs. points)
7pm, Sign-in sheet for credit – Find Raquel with bright orange clipboard
Moon Phases, Due Oct. 12 (10 obs. points)
Moon visible times: (Moonrise and Moonset)
Phone Apps: Phases of the Moon Free (android) & Lunar Phase (iphone)
Star Gazing, Telescopes & Moon Craters, Due Dec. 12 (60 obs. points)
Look at class calendar and pick a date option that works for you – only do once
Point out Student Success Day and look for website. Work on Sunset and Moon Phases – more info next slide
Go through Sunset Part 1 – didn’t cover that Tuesday! More info on next slide too.

24. Homework
D2L Quizzes 4 available – quiz 3 on Cycles of the Sky (Moon); quiz 4 on Copernican Revolution (today and Tuesday)
Test 1 on Sep. 19 (bring pencil, calculator optional or some provided)
About 60 multiple choice questions
Best test prep: Review Study Points & D2L quizzes
Closed notes and textbook for test
Grades are updated weekly, usually Wednesday or Thursday on website
Keep up with Study Points (flashcards)