Today’s Comments

1. Today’s Comments D2L Week 4 Quiz available for extra credit Sunset – Part 1 Due 9/25/14 (in 1 week) Test 1 on Sept. 30. Special tutor session with Gustavo: Thurs, 9/25/14, 4-6pm, Room T3480 Moon Observations: Craters, Phases & Motion Moon Craters: binoculars to borrow in my office or go view through a telescope Moon Phases Moon visible times: (Moonrise and Moonset) http://www.timeanddate.com/moon/usa/minneapolis Phone App: Phases of the Moon Free Moon Motion: times in file on calendar Safe Sun makeup chance (half of the points) on 10/23/14 for partial solar eclipse viewing at Eagle Lake Observatory 4-6:30pm. Stay later to complete Telescope Observation.

2. Prior to 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

3. Everything orbits around… Geocentric Model* (from Aristotle, 384-322BC) Earth Sun Heliocentric Model* (from Copernicus, 1473-1543AD)

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

5. Prior to the Copernican Revolution – Greek Astronomy Hesiad, Works and Days • ... 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 calendars synchronized.

6. Prior to the Copernican Revolution – Greek Astronomy Greeks ~Fifth Century BC • What is the sun? Fire? • Tiny lights in the sky? • Why do 7 lights wander among the others? (7 Planetes*) science.msfc.nasa.gov/ ssl/pad/solar/surface.htm imagine.gsfc.nasa.gov/.../ news/22apr02.html http://artsci.shu.edu/physics/1007/retro2.gif

7. 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 others • Already thinking geocentric http://library.thinkquest.org/C0126626/fate/geocentric.jpg

8. 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

9. Prior to the Copernican Revolution – Greek Astronomy Aristotle ~350 BC • Plato’s student • Earth: Corrupt, changeable, imperfect (separation of heavens and Earth) • Arguments for geocentric model* No parallax of stars* and Moon would be left behind* • Parallax is the apparent change in position of an object due to the change in position of the observer • Parallax thumb demonstration

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

11. 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* (retrograde motion)*

12. Retrograde Motion Sometimes planets moved backwards against the background of stars. The retrograde (westward) motion of the planets

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

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

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

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

17. 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

18. Prior to the Copernican Revolution – Greek Astronomy Dark Ages in Europe (5th to 15th centuries AD) • Roman libraries sacked • Often violent mix of Latin and Arabic cultures • Plague, famine, war • Islamic Golden Age of Science Long time between Ptolemy ~140 AD to Copernicus ~1500 AD.

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

20. Today’s Comments D2L Week 4 Quiz available for extra credit Sunset – Part 1 Due 9/25/14 (in 1 week) Test 1 on Sept. 30. Special tutor session with Gustavo: Thurs, 9/25/14, 4-6pm, Room T3480 Moon Observations: Craters, Phases & Motion Moon Craters: binoculars to borrow in my office or go view through a telescope Moon Phases Moon visible times: (Moonrise and Moonset) http://www.timeanddate.com/moon/usa/minneapolis Phone App: Phases of the Moon Free Moon Motion: times in file on calendar Safe Sun makeup chance (half of the points) on 10/23/14 for partial solar eclipse viewing at Eagle Lake Observatory 4-6:30pm. Stay later to complete Telescope Observation.