Galileo and the New Cosmology

1. Galileo and the New Cosmology David Banach Department of Philosophy

2. How sweet the moonlight sleeps upon this bank!Here will we sit and let the sounds of musicCreep in our ears: soft stillness and the nightBecome the touches of sweet harmony.Sit, Jessica. Look how the floor of heavenIs thick inlaid with patines of bright gold:There's not the smallest orb which thou behold'stBut in his motion like an angel sings,Still quiring to the young-eyed cherubins;Such harmony is in immortal souls;But whilst this muddy vesture of decayDoth grossly close it in, we cannot hear it

3. The Music of the SpheresMerchant of Venice, Act V • How sweet the moonlight sleeps upon this bank!Here will we sit and let the sounds of musicCreep in our ears: soft stillness and the nightBecome the touches of sweet harmony.Sit, Jessica. Look how the floor of heavenIs thick inlaid with patines of bright gold:There's not the smallest orb which thou behold'stBut in his motion like an angel sings,Still quiring to the young-eyed cherubins;Such harmony is in immortal souls;But whilst this muddy vesture of decayDoth grossly close it in, we cannot hear it

4. Two Golden Ages of Astronomy

5. Ptolemy (100-170AD)

6. Ptolemaic Heliocentric Universe

7. Terrestrial and Heavenly Spheres

8. Cross Section

9. Terrestrial Spheres

10. Terrestrial Motion • Four Elements: Earth, Air, Fire, Water • Each Element has a natural place, its own home sphere. • All objects move to reach their goal or fulfill their potential. • Straight line, rectilinear, motion. • Less perfect.

11. Crystalline spheres

12. Heavenly Spheres • Made of a fifth Element: Aether • More perfect, circular motion • Moves in imitation of God’s perfect thought motion (Thought thinking itself). • Moved by final causality or purpose, not through contact. • All things move to the unmoved mover, just as a lover moves toward their beloved.

13. Moral structure of the universe

14. Dante’s Divine Comedy (~1300)

15. Aristotle’s Universe

16. Great Chain of Being

17. A place for everything and everything in its place

18. Parallel Hierarchies in Different Realms

19. Moral structure of the universe

20. II. Saving the Appearances • Ancient and Medieval Astronomy aimed at geometrically constructing a model of the universe that reproduced, or predicted, or “saved” the appearances we observe in the heavens. • Two kinds of motions: • 1. Diurnal (Daily) • 2. Yearly

21. Diurnal (east to west, every 24 hours)

22. Diurnal Motion of Stars

23. Diurnal Motion of Stars

24. Seasonal Motions: Stars-none Planets- Wanderers, West to East, Slow

25. Ecliptic and the Zodiac Ecliptic- Path along which the sun moves in the heavens. Tilted 23 degrees. Zodiac- Ecliptic divided into 12 sections named for the constellation in each section.

26. Sun Moving through the Zodiac

27. Two Motion of Planets • Diurnal: By participation in Motion of Heavens • Seasonal: Proper Motion of the sphere of each planet slower and from west to east.

28. A little complication : Retrogression

29. Ptolemy’s Solution: Deferents and Epicycles

30. Ptolemy’s Solution: Deferents and Epicycles

31. Music of the Spheres

32. Music of the Spheres

33. Copernicus’s System

34. Copernicus’s System

35. Copernicus’s System

36. Copernicus’s View of Retrogression

37. Copernicus’s View of Retrogression Mars Venus

38. Copernicus’s View of Retrogression

39. Uses of the Systems • Astrology: All Major astronomers of the day did composed Astrological Carts.

40. Uses of the Systems • Calendar: Introduction of Gregorian Calendar: Pope Gregory XIII decreed that the day after October 4, 1582 would be October 15, 1582

41. Comparison of Complexity of the two views

42. Tycho Brahe (1546-1601)

43. Tycho Brahe’s System

44. Johannes Kepler (1571 – 1630) Equal areas in equal time R^3 = T^2

45. Dialogues Concerning the Two Principal Systems of the World • (1632) http://dbanach.com/galileo • Salviati = Galileo (Copernicus) • Sagredo = Learned Layman • Simplico = Aristotelian Professor (Ptolemy)

46. Galileo on Trial (1633)

47. Arguments for Copernican Model • Immense magnitude of the starry sphere. It makes more sense to have the smaller sphere move rather than the larger.  • Contrary Motions. Having the heavens moves involves attributing to the planets two contrary motions (diurnal and seasonal) • Speed of Motion. The greater the size of the sphere, the longer it takes to revolve. • Different Sizes of Stars’s orbits. The stars move in circles of different sizes depending on their nearness to the poles. • Change of orbits. These circles have changed as the stars have moved their positions in the skies over great periods of time. • Strength of Sphere holding stars. The solidity of the sphere in which the stars are embedded to keep their motions regular also strains belief. • Great motion of Heavens would sweep Earth along as well. The motion of the stars which carries all the other spheres along with it, would surely move the earth as well.

48. Different Sizes of Stars’s orbits. The stars move in circles of different sizes depending on their nearness to the poles.

49. Change of orbits. These circles have changed as the stars have moved their positions in the skies over great periods of time.

50. Contrary Motions Two Motions: Which is the Natural Motion? How can it hear two different songs?