Bit of Administration.

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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 d the Sun Maximum Elongation - furthest angular distance from the Sun Mercury 28 o Venus 46 o

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 d the Sun Roughly equal amounts of time in each direction Maximum Elongation - furthest angular distance from the Sun Mercury 28 o Venus 46 o Superior Planets Mars, Jupiter, Saturn Most of time, move from west to east relative to the stars - Every years motion becomes east to west for 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 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 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 Early Greek Astronomy Aristotle 350 BC Right Reasoning, Right Conclusion! 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 EarthE Spherical Earth Wrong Reasoning, Shadow is round during lunar eclipses Right Conclusion! Travel in latitude changes the positions of the stars Wrong Reasoning, Elephants were found both to the east in India and to the west in Morocco Wrong Conclusion! 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 ax was seen Cosmology of the Spheres Right Reasoning, Wrong Conclusion!

15 Aristotle 350 BC Early Greek Astronomy 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)