Bit of Administration ….

2. Bit of Administration …. • Observing Lab 1 • Due on Monday, February 9 • ONLY if NO clear nights through next Sunday, can be turned in on Wednesday, February 11

3. Planetary Motions • Inferior Planets Mercury and Venus • In the sky, shuttle back and forth (eastward and westward) around the Sun • Maximum Elongation - furthest angular distance from the Sun • Mercury 28o • Venus 46o

4. ConcepTest! Venus can be observed at midnight from Madison. A) True B) False

5. Planetary Motions • Inferior Planets Mercury and Venus • In the sky, shuttle back and forth (eastward and westward) around the Sun • Roughly equal amounts of time in each direction • Maximum Elongation - furthest angular distance from the Sun • Mercury 28o • Venus 46o • Superior Planets Mars, Jupiter, Saturn … • Most of time, move from west to east relative to the stars • Every 1-2 years motion becomes east to west for 1-2 months • Retrograde Loop

6. Celestial Motions - Summary • Daily Motion • Player - All objects in the sky • Direction - East to West • Timescale 24 hours (“day”) • Lunar Motion • Player - Moon • Direction - West to East • Timescale 29 days (“month”) • Solar Motion • Player - Sun • Direction - West to East • Timescale 365 days (“year”) • Planetary Motion • Inferior Planets Mercury, Venus • Direction - Roughly equal west to east and east to west • Timescale - Months • Superior Planets Mars, Jupiter, Saturn, Uranus, Neptune, Pluto and the asteroids • Mostly west to east (“prograde”) with brief (few months) east to west (“retrograde”) loops • Timescale - from two years (Mars) to hundreds of years (Pluto and beyond)

7. ConcepTest! You have all seen Mars very nearly overhead in the past few nights. Where will Mars be in the sky in April? A) Nearer to the western horizon. B) Nearly overhead, in essentially the same place. C) Nearer to the eastern horizon. WARNING! This is a hard question!

8. Earliest Civilizations

9. Earliest Civilizations • Direction Finding • Polaris • Gnomons • Time Keeping • Time of Day • Fundamentally tied to the sky, typically the Sun • Time of Year • Fundamentally tied to the position of Sun • relative to the stars or the horizon

10. Early Greek Astronomy • Thales and the Ionian School 7th Century BC • There exists an underlying order to the universe • Removes the influence of the supernatural • Liberating act of faith, no compelling evidence • It is possible for ordinary mortals to understand the order with rational thought. • First sense of objectivity and separation from the order • Allows the question “How is the Universe organized” • What is basic to understanding the structure and the processes?

11. 1 1.414213 ….. 1 Early Greek Astronomy • Pythagorus 500 BC • Mathematics is basic to reality • Mathematics was reality, not just description of reality • The universe was understandable as harmonious relations of numbers • Developed abstract math and deductive reasoning • Spherical heavenly bodies, including the Earth • Purest geometrical form • Never disappeared from Greek thought • Cosmology based on ratios of integers • “Harmony of the spheres” • But

12. Early Greek Astronomy • Plato 400 BC • Geometric Ideals Underly Reality • Uniform Circular Motion • Circular Motion at Constant Speed • “No beginning, no end, no change” • Construct a geometric representation of celestial motions using only combinations of uniform circular motions about the central fixed earth • Senses are Imperfect and Unreliable • Observation is not important - reason reigns supreme • Qualitative agreement is acceptable

13. Early Greek Astronomy • Eudoxus 400 BC

14. Right Reasoning, Right Conclusion! Wrong Reasoning, Right Conclusion! Wrong Reasoning, Wrong Conclusion! Right Reasoning, Wrong Conclusion! Early Greek Astronomy • Aristotle 350 BC • Lunar Phases and Eclipses • Argued that Sun was further than the moon • Eclipses • Slower motion in the sky • Argued that Moon shines by reflected light • Intellectual leap toward relationships that are independent of Earth • Spherical Earth • Shadow is round during lunar eclipses • Travel in latitude changes the positions of the stars • Elephants were found both to the east in India and to the west in Morocco • Only spherical shape would allow motion to the center to be straight down • Motion of Earth • Realized that daily motion could be either earth or celestial sphere spinning • Considered heliocentric universe, but rejected because no parallax was seen • Cosmology of the Spheres

15. Early Greek Astronomy • Aristotle 350 BC • Physics • The universe as a machine • All vertical motion driven by inclination to natural places • The natural place of Earth was toward the center of the Universe/Earth • First theory of gravity! • Chemistry • Earth, Air, Fire, Water - the stuff of the human world • Quintessence - the stuff of the celestial bodies • Encyclopedic Treatises on Nearly Every Field For 2000 years the Universe was Aristotelian (though primary impact was after 1200 AD)