Bit of Administration ….Bit of Administration ….

• Observing Lab 1Observing Lab 1– Due on Monday, February 9Due on Monday, February 9– ONLY if NO clear nights through next Sunday, can ONLY if NO clear nights through next Sunday, can

be turned in on Wednesday, February 11be turned in on Wednesday, February 11

Planetary Motions

• Inferior Planets Mercury and VenusInferior Planets Mercury and Venus– In the sky, shuttle back and forth (eastward and westward) around the SunIn the sky, shuttle back and forth (eastward and westward) around the Sun– Maximum Elongation - furthest Maximum Elongation - furthest angularangular distance from the Sun distance from the Sun

• Mercury 28Mercury 28oo

• Venus 46Venus 46oo

Venus can be observed at midnight from Madison. Venus can be observed at midnight from Madison.

A) TrueA) True B) FalseB) False

ConcepTest!ConcepTest!

Planetary Motions

• Inferior Planets Mercury and VenusInferior Planets Mercury and Venus– In the sky, shuttle back and forth (eastward and westward) around the SunIn the sky, shuttle back and forth (eastward and westward) around the Sun

• Roughly equal amounts of time in each directionRoughly equal amounts of time in each direction

– Maximum Elongation - furthest Maximum Elongation - furthest angularangular distance from the Sun distance from the Sun• Mercury 28Mercury 28oo

• Venus 46Venus 46oo

• Superior Planets Mars, Jupiter, Saturn …Superior Planets Mars, Jupiter, Saturn …– Most of time, move from west to east Most of time, move from west to east relative to the starsrelative to the stars- Every 1-2 years motion becomes east to west for 1-2 monthsEvery 1-2 years motion becomes east to west for 1-2 months

- Retrograde LoopRetrograde Loop

Celestial Motions - Summary• Daily MotionDaily Motion

– Player - All objects in the skyPlayer - All objects in the sky– Direction - East to WestDirection - East to West– Timescale 24 hours (“day”)Timescale 24 hours (“day”)

• Lunar MotionLunar Motion– Player - MoonPlayer - Moon– Direction - West to EastDirection - West to East– Timescale 29 days (“month”)Timescale 29 days (“month”)

• Solar MotionSolar Motion– Player - SunPlayer - Sun– Direction - West to EastDirection - West to East– Timescale 365 days (“year”)Timescale 365 days (“year”)

• Planetary MotionPlanetary Motion– Inferior Planets Mercury, VenusInferior Planets Mercury, Venus

• Direction - Roughly equal west to east and east to westDirection - Roughly equal west to east and east to west• Timescale - MonthsTimescale - Months

– Superior Planets Mars, Jupiter, Saturn, Uranus, Neptune, Pluto and the asteroidsSuperior Planets Mars, Jupiter, Saturn, Uranus, Neptune, Pluto and the asteroids• Mostly west to east (“prograde”) Mostly west to east (“prograde”) with brief (few months) east to west (“retrograde”) loopswith brief (few months) east to west (“retrograde”) loops• Timescale - from two years (Mars) to hundreds of years (Pluto and beyond)Timescale - from two years (Mars) to hundreds of years (Pluto and beyond)

You have all seen Mars very nearly overhead in the past few You have all seen Mars very nearly overhead in the past few nights. Where will Mars be in the sky in April? nights. Where will Mars be in the sky in April?

A) Nearer to the western horizon.A) Nearer to the western horizon. B) Nearly overhead, in essentially the same place.B) Nearly overhead, in essentially the same place. C) Nearer to the eastern horizon.C) Nearer to the eastern horizon.

WARNING! This is a hard question!WARNING! This is a hard question!

ConcepTest!ConcepTest!

Earliest CivilizationsEarliest Civilizations

Earliest CivilizationsEarliest Civilizations

• Direction FindingDirection Finding• PolarisPolaris• GnomonsGnomons

• Time KeepingTime Keeping• Time of DayTime of Day

• Fundamentally tied to the sky, typically the SunFundamentally tied to the sky, typically the Sun

• Time of YearTime of Year• Fundamentally tied to the position of Sun Fundamentally tied to the position of Sun relative to the stars or the horizonrelative to the stars or the horizon

Early Greek AstronomyEarly Greek Astronomy

• Thales and the Ionian School 7th Century BCThales and the Ionian School 7th Century BC– There exists an underlying order to the universeThere exists an underlying order to the universe

• Removes the influence of the supernaturalRemoves the influence of the supernatural• Liberating act of faith, no compelling evidenceLiberating act of faith, no compelling evidence

– It is possible for ordinary mortals to understand the order with It is possible for ordinary mortals to understand the order with rational thought.rational thought.

• First sense of objectivity and separation from the orderFirst sense of objectivity and separation from the order

– Allows the question “How is the Universe organized”Allows the question “How is the Universe organized”• What is basic to understanding the structure and the processes?What is basic to understanding the structure and the processes?

• Pythagorus 500 BCPythagorus 500 BC– Mathematics is basic to realityMathematics is basic to reality

• Mathematics Mathematics waswas reality, not just description of reality reality, not just description of reality• The universe was understandable as harmonious relations of numbersThe universe was understandable as harmonious relations of numbers• Developed abstract math and deductive reasoningDeveloped abstract math and deductive reasoning

– Spherical heavenly bodies, including the EarthSpherical heavenly bodies, including the Earth• Purest geometrical formPurest geometrical form• Never disappeared from Greek thoughtNever disappeared from Greek thought

– Cosmology based on ratios of integers Cosmology based on ratios of integers • ““Harmony of the spheres”Harmony of the spheres”• ButBut

Early Greek AstronomyEarly Greek Astronomy

11

11

1.414213 …..1.414213 …..

• Plato 400 BCPlato 400 BC

– Geometric Ideals Underly RealityGeometric Ideals Underly Reality• Uniform Circular MotionUniform Circular Motion

– Circular Motion at Constant SpeedCircular Motion at Constant Speed– ““No beginning, no end, no change”No beginning, no end, no change”– Construct a geometric representation of celestial motions using only combinations of Construct a geometric representation of celestial motions using only combinations of

uniform circular motions about the central fixed earthuniform circular motions about the central fixed earth

– Senses are Imperfect and UnreliableSenses are Imperfect and Unreliable• Observation is not important - reason reigns supremeObservation is not important - reason reigns supreme

– Qualitative agreement is acceptableQualitative agreement is acceptable

Early Greek AstronomyEarly Greek Astronomy

• Eudoxus 400 BCEudoxus 400 BC

Early Greek AstronomyEarly Greek Astronomy

• Aristotle 350 BCAristotle 350 BC

– Lunar Phases and EclipsesLunar Phases and Eclipses• Argued that Sun was further than the moonArgued that Sun was further than the moon

– EclipsesEclipses– Slower motion in the skySlower motion in the sky

• Argued that Moon shines by reflected lightArgued that Moon shines by reflected light– Intellectual leap toward relationships that are independent of EarthIntellectual leap toward relationships that are independent of Earth

– Spherical EarthSpherical Earth• Shadow is round during lunar eclipsesShadow is round during lunar eclipses• Travel in latitude changes the positions of the starsTravel in latitude changes the positions of the stars• Elephants were found both to the east in India and to the west in MoroccoElephants 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 downOnly spherical shape would allow motion to the center to be straight down

– Motion of EarthMotion of Earth• Realized that daily motion could be either earth or celestial sphere spinningRealized that daily motion could be either earth or celestial sphere spinning• Considered heliocentric universe, but rejected because no parallax was seenConsidered heliocentric universe, but rejected because no parallax was seen

– Cosmology of the SpheresCosmology of the Spheres

Early Greek AstronomyEarly Greek Astronomy

Right Reasoning, Right Conclusion!

Wrong Reasoning, Right Conclusion!

Right Reasoning, Wrong Conclusion!

Wrong Reasoning, Wrong Conclusion!

• Aristotle 350 BCAristotle 350 BC

– PhysicsPhysics• The universe as a machineThe universe as a machine• All vertical motion driven by inclination to natural places All vertical motion driven by inclination to natural places • The natural place of Earth was toward the center of the Universe/EarthThe natural place of Earth was toward the center of the Universe/Earth

– First theory of gravity!First theory of gravity!

– ChemistryChemistry• Earth, Air, Fire, Water - the stuff of the human worldEarth, Air, Fire, Water - the stuff of the human world• Quintessence - the stuff of the celestial bodiesQuintessence - the stuff of the celestial bodies

– Encyclopedic Treatises on Nearly Every FieldEncyclopedic Treatises on Nearly Every Field

For 2000 years the Universe was AristotelianFor 2000 years the Universe was Aristotelian(though primary impact was after 1200 AD)(though primary impact was after 1200 AD)

Early Greek AstronomyEarly Greek Astronomy