1. C/2002 T7 (LINEAR)

2. Bit of Administration …. HomeworksHomeworks –Due in lecture or by 3:45 on Friday at 6515 Sterling –Error in Question 5: replace ‘3’ with ‘4’ Office HoursOffice Hours –M 3:30-5:30 ==> 3:30 - 4:35 (Honors at 4:35) Observing LabObserving Lab –Continue Lab 3 –Higher quality of recording data “You can’t get these labs wrong if you observe carefully”“You can’t get these labs wrong if you observe carefully”

3. Hipparchus, The Great Observer Hipparchus150 BC (Island of Rhodes)Hipparchus150 BC (Island of Rhodes) –Cataloged Positions and Brightnesses of 850 Stars –Length of Month and Year, With Errors Year accurate to 6 minutes, Month accurate to secondsYear accurate to 6 minutes, Month accurate to seconds –Precession (“of the equinoxes”)

4. Precession

5. Hipparchus Hipparchus150 BC (Island of Rhodes)Hipparchus150 BC (Island of Rhodes) –Cataloged Positions and Brightnesses of 850 Stars –Length of Month and Year, With Errors Year Accurate to 6 minutes, Month accurate to secondsYear Accurate to 6 minutes, Month accurate to seconds –Precession – Non-Uniform Motion of Sun (and Moon) Solar Motion is faster in (northern) winter Solar Motion is faster in (northern) winter

6. Evolution of Greek Cosmologies Platonic - Earth-Centered, Uniform Circular Motion Winter Summer Hipparchus - Eccentric Circle, Uniform Circular Motion Summer Winter Epicycles Hipparchus - Earth-Centered, Uniform Circular Motion Deferent

7. Evolution of Greek Cosmologies Hipparchus150 BC (Island of Rhodes)Hipparchus150 BC (Island of Rhodes) –Cataloged Positions and Brightnesses of 850 Stars –Length of Month and Year, With Errors Year Accurate to 6 minutes, Month accurate to secondsYear Accurate to 6 minutes, Month accurate to seconds –Precession – Non-Uniform Motion of Sun and Moon Solar motion is faster in (northern) winter Solar motion is faster in (northern) winter – The “Eccentric Circle” Primacy of observation over dogma Primacy of observation over dogma Inter-relation of observation and theory Inter-relation of observation and theory The role of the aesthetic in understanding the universe The role of the aesthetic in understanding the universe

8. Evolution of Greek Cosmologies Ptolemy140 AD “The Great Synthesizer”Ptolemy140 AD “The Great Synthesizer” –Almagest 13 volumes, source of most Greek astronomy –Assume Uniform Circular MotionUniform Circular Motion Earth Spherical, Stationary, Near CenterEarth Spherical, Stationary, Near Center –Account For Daily Motion from East to WestDaily Motion from East to West Prograde (West to East) Motions of Sun, Moon, PlanetsPrograde (West to East) Motions of Sun, Moon, Planets Retrograde Motion of PlanetsRetrograde Motion of Planets Mercury < 28 o, Venus < 46 o from SunMercury < 28 o, Venus < 46 o from Sun Non-Uniformity in Rates of Prograde MotionsNon-Uniformity in Rates of Prograde Motions And everything else!And everything else!

9. E M V S M J S 46 o 28 o Daily

10. Evolution of Greek Cosmologies Ptolemy140 AD “The Great Synthesizer”Ptolemy140 AD “The Great Synthesizer” –Epicycles ==> Retrograde Motion

11. Evolution of Greek Cosmologies Ptolemy140 AD “The Great Synthesizer”Ptolemy140 AD “The Great Synthesizer” –Epicycles ==> Retrograde Motion 5/1 3 1 4 2 4 3 2 1 1/1

12. Evolution of Greek Cosmologies Ptolemy140 AD “The Great Synthesizer”Ptolemy140 AD “The Great Synthesizer” –Epicycles ==> Retrograde Motion

13. E M V S M J S Daily

14. Evolution of Greek Cosmologies Ptolemy140 AD “The Great Synthesizer”Ptolemy140 AD “The Great Synthesizer” –Equant ==> Non-Uniform Motions Equant Uniform Angular Motion

15. Evolution of Greek Cosmologies Ptolemy140 AD “The Great Synthesizer”Ptolemy140 AD “The Great Synthesizer” –Equant ==> Non-Uniform Motions

16. Evolution of Greek Cosmologies Ptolemy140 AD “The Great Synthesizer”Ptolemy140 AD “The Great Synthesizer” –Almagest 13 volumes, source of most Greek astronomy –Assume Uniform Circular MotionUniform Circular Motion Earth Spherical, Stationary, Near CenterEarth Spherical, Stationary, Near Center –Account For Daily Motion from East to WestDaily Motion from East to West Prograde (West to East) Motions of Sun, Moon, PlanetsPrograde (West to East) Motions of Sun, Moon, Planets Retrograde Motion of PlanetsRetrograde Motion of Planets Mercury < 28 o, Venus < 46 o from SunMercury < 28 o, Venus < 46 o from Sun Non-Uniformity in Rates of Prograde MotionsNon-Uniformity in Rates of Prograde Motions And everything else!And everything else! Ptolemaic predictions were only accurate to about 5 o A collection of recipes - not an Aristotelian machine.

17. The Transition to A Heliocentric Cosmology No fundamentally new ideas in astronomy for 1400 yr; Greek astronomy preserved in Islamic world during the European Dark Ages.No fundamentally new ideas in astronomy for 1400 yr; Greek astronomy preserved in Islamic world during the European Dark Ages. Copernicus1500 ADCopernicus1500 AD –De Revolutionibus Orbium Coelstium 1543 (On the Revolution of the Celestial Spheres) (On the Revolution of the Celestial Spheres) –Motivations Philosophical ObjectionsPhilosophical Objections –Ptolemaic cosmology wasn’t a machine that could be built –Equant violated Uniform Circular Motion –Fundamentally an Aristotelian world view NOT inaccuracy or inadequacy of geocentric systemNOT inaccuracy or inadequacy of geocentric system NOT Sun “should” be at the centerNOT Sun “should” be at the center –Assumptions HeliocentricHeliocentric Earth rotates once every 24 hoursEarth rotates once every 24 hours Earth-Sun distance << Earth-Stars distanceEarth-Sun distance << Earth-Stars distance Uniform Circular MotionUniform Circular Motion

18. M S J S M E Not to scale! V

19. The Transition to A Heliocentric Cosmology Copernicus1500 ADCopernicus1500 AD –Daily Motion due to Earth rotation –Solar Motion due to Earth revolution around the Sun –Prograde Motion of Moon and Planets due to their orbital motions More correctly for the planets, their motions relative to the moving EarthMore correctly for the planets, their motions relative to the moving Earth –Retrograde Motion of Planets

20. CopernicusRetrograde Motion of Outer Planets

21. The Transition to A Heliocentric Cosmology Copernicus1500 ADCopernicus1500 AD –Daily Motion due to Earth Rotation –Solar Motion due to Earth Revolution –Prograde Motion of Moon and Planets due to their Orbital Motion –Retrograde Motion of Planets –Maximum Elongations of Mercury and Venus E S V M 46 o 28 o

22. The Transition to A Heliocentric Cosmology Copernicus1500 ADCopernicus1500 AD –Daily Motion due to Earth Rotation –Solar Motion due to Earth Revolution –Prograde Motion of Moon and Planets due to their Orbital Motion –Retrograde Motion –Maximum Elongations of Mercury and Venus –Geometric Distances to the Planets (example for Venus) E S M 46 o V V E S VS = ES * sin 46 o = (1 AU) * sin 46 o 1 Astronomical Unit = Earth-Sun Distance

23. The Transition to A Heliocentric Cosmology Copernicus1500 ADCopernicus1500 AD –Daily Motion due to Earth Rotation –Solar Motion due to Earth Revolution –Prograde Motion of Moon and Planets due to their Orbital Motion –Retrograde Motion –Maximum Elongations of Mercury and Venus –Geometric Distances to the Planets (example for Venus) PlanetCopernicusModern Mercury 0.38 0.39 Venus 0.72 0.72 Earth 1.00 1.00 Mars 1.52 1.52 Jupiter 5.22 5.07 Saturn 9.07 9.54

24. The Transition to A Heliocentric Cosmology Copernicus1500 ADCopernicus1500 AD –Daily Motion due to Earth Rotation –Solar Motion due to Earth Revolution –Prograde Motion of Moon and Planets due to their Orbital Motion –Retrograde Motion –Maximum Elongations of Mercury and Venus –Geometric Distances to the Planets (example for Venus) –Star Very Far Away No observed parallaxNo observed parallax Summer Winter Epicycles –Non-Uniform Motion of Sun, Moon and Planets Retained uniform circular motion!Retained uniform circular motion!

25. M S M S E Not to scale! V J

26. The Transition to A Heliocentric Cosmology Copernicus1500 ADCopernicus1500 AD –Daily Motion due to Earth Rotation –Solar Motion due to Earth Revolution –Prograde Motion of Moon and Planets due to their Orbital Motion –Retrograde Motion –Maximum Elongations of Mercury and Venus –Geometric Distances to the Planets (example for Venus) –Star Very Far Away No observed parallaxNo observed parallax –Non-Uniform Motion of Sun, Moon and Planets In the 1500’s, the Copernican system did not predict positions better than the highly refined Ptolemaic system The Copernicans had no proof - the arguments were aesthetic and religious