Post Galilean Astronomy

1. Post Galilean Astronomy Kicking and Screaming into the Modern Age This logo denotes A102 appropriate

2. Old ideas die hard • Giambattista Riccioli (1598-1671) in 1651 publishes Almagestum Novum (The New Almagest) • Mercury, Venus, Mars orbit the Sun • Sun, Jupiter, Saturn orbit Earth • 20 arguments for, 77 against heliocentism • Geocentric • Tychonean • Heliocentric

3. Copernicanism prompts questions: • If Earth is not the center, then what? • How can natural motion be explained? • If the Earth is a celestial body, is there really a difference between terrestrial motion and celestial Physics? • What is really true? • By 1700, the old scholasticism gives way to more modern epistemologies, and away from southern to northern Europe

4. Astronomy begins to look familiar • Galileo’s telescope • Seeing things as they really are • Seeing more than ever imagined • Kepler’s Laws • Application of protocalculus • Slow abandonment of old ideas

5. The known planets in the 17th Century

7. And What Is This? • Giovanni Battista Hodierna • 1654 • Noted in his “De AdmirandisCoeliCharacteribus” • His sketch

8. The evidence of the new technologies leads to Changes in thinking from 1600-1700

9. Aristotelian Scholastism • A mixture of ancient Greek and medieval scholasticism, dominant in 1600 universities • Four components of causality • Material cause: stuff has to exist in the first place • Formal cause: what the stuff becomes • Efficient cause: somebody/something has to do the forming • Final cause: the reason for the action

10. Aristotelian physics: • Distinction between terrestrial and celestial physics • This has now changed to coupling Earth and sky • Every body has a rightful place and must move naturally (up or down) toward it • Newton finally buries this concept • Material composition determines where that rightful place is • Earth -- center of universe • Water -- above earth; below air • Air -- above water; below fire • Fire -- boundary of terrestrial and celestial realm • Quintessence -- natural motion is at a constant speed in perfect circles

11. The Disputatio • A hierarchy of belief or acceptance of ideas; • Authority: supernatural (God) first, then natural, usually ancient Greek • Reason: Aristotelian causality • Experience • These are the intellectual descendants of medieval scholasticism and the influence of Thomas Aquinas

12. Francis Bacon • Contemporary of Galileo, Kepler • Not an astronomer • Sets the tone for 17th C inquiry in his New Organon (new way to organize thinking) • Knowledge is human power • Science is separate from theology • Science should always be tested through experimentation • Science is an ongoing, cumulative activity • Galileo echoed this sentiment in this quote: • “The Bible tells how to go to Heaven, not how the heavens go”

13. The Royal Society • Founded 1660 in London • A reaction to the continued Aristotelian curriculum at Oxford and Cambridge • Initially very much influenced by William Gilbert’s ‘magnetic philosophy’, that celestial motion is caused by magnetism • No theories of gravity are extant • “When all you have is a hammer, everything looks like a nail”

14. Rene Descartes 1596-1650 • French Mathematician/Philosopher • Cartesean coordinates • Cogito ergo sum • Believed like Averroes that God (the Great Clockmaker) created the Universe and then just let it run without daily adjustments • Afraid in Catholic France to embrace Copernicanism publicly • Remembered Bruno’s fate • Couched his ideas in a hypothetical distant planet

15. Heliocentric • The cosmos was filled with unseen matter that flowed like a river, carrying the stars and planets along • Emptiness is impossible – “nature abhors a vacuum” • Motion occurs due to physical contact • Orbits were vortices of this celestial fluid, the luminiferousaether

16. Stars at the center of the ‘whirlpools’ • Planets carried around • Comets swoop through, unbound to any particular star • Not Gilbert’s magnetic forces; fluids! • “When all you have is a hammer, everything looks like a nail”

17. Even earthly motion fits the vortex model, according to Descartes

18. Isaac Newton • Born in England the year Galileo dies in Woolsthorpe-by-Colsterworth • 300 years before Steven Hawking is born: 1642 • Father dies before he is born • A sickly child, given up by his mother (remarried) to her parents at age 2

19. Early Years* • Newton began his schooling in the village schools and later was sent to Grantham Grammar School • Naturally he was the top student! • At Grantham he lodged with the local apothecary, William Clarke • He became engaged to the apothecary's stepdaughter, Anne Storey, before he went off to Cambridge University at the age of 19 • As Newton became engrossed in his studies, the romance cooled and Miss Storey married someone else. • It is said he kept a warm memory of this love, but Newton had no other recorded 'sweethearts' and never married. *Men of Mathematics E.T. Bell (1937, Simon and Schuster)

20. Schooling • Entered Trinity College (Cambridge) in 1661 • Still taught Aristotelian physics • Students discussed Galileo and Kepler, but not in class • Brilliant (geeky) student • Devoted to the Cartesian model of the universe • 1665 school closes because of the plague • Newton invents calculus (!) to solve a problem

21. Professorship • School reopens 1667 • Newton elected fellow, then in 1669 becomes a professor of mathematics • Studies Descartes’ theory of light as motion in a medium • Shows white light is made of all colors

22. Motion • Newton's (Cartesian) ideas on falling bodies (ca. 1664): • ...so may the gravitating attraction of the Earth be caused by the continuall condensation of some ... aethereall Spirit, not of the main body of flegmaticaether, but of something very thinly and subtily diffused through it .. • 1679: Debate in the Royal Society on the elliptical motion of planets • Newton was still working with vortices • Robert Hooke: • “...of compounding the celestiall motions of the planetts of a direct motion by the tangent (inertial motion) and an attractive motion towards the centrall body ... my supposition is that the Attraction always is in a duplicate proportion to the Distance from the Center Reciprocall...

23. Newton to the Rescue • 1684: Edmund Halley goes to Newton, asks what orbital shape would an inverse square force yield? • An ellipse! • Newton has already done the problem • The reason he invented calculus during his forced vacation in 1665 • Newton sends papers off to Halley who finances the project • He goes into seclusion for 18 months and writes the Principia Mathematica (1687) • THE book on Physics, even now

24. Three Laws of Motion • An object moves in constant motion in a straight line unless acted upon by an external force (inertia) • The acceleration of an object depends directly on the applied force and inversely upon its mass • For every action there is an equal and opposite reaction

25. And the answer is: • The solution to the ellipse question combines Kepler’s third law, calculus, and Newton’s laws of motion • The Law of Universal Gravitation: every mass in the universe attracts every other mass with a force equal to the product of their masses and inversely proportional to the square of the distance between them • Newton had to abandon a matter-filled universe for one of forces across empty space

26. Consequences • How gravity makes orbits • The apple myth • Newton offered no explanation as to why gravity worked this way • 100 years later Coulomb would use Newton’s ideas for electric force

27. Illustration of Newton’s Laws

28. War with Leibniz over calculus • Newton’s infinite series (not far from Kepler’s swept areas) • Fluxions • Developed before but published after Leibniz • Wilhelm Leibniz differentials • Bitter dispute • Delayed acceptance of Newtonian Physics into continental Europe

29. Newton’s later life • Studies alchemy extensively • Looks for scientific revelations in scripture • Leibniz beat him up over this • Pursues the corpuscular theory of light • Optics published in 1704 • Lucasian Chair in Mathematics at Cambridge • Hawking’s position today • Warden of the Mint 1699 • Ceases to do much science • Concentrates on finding counterfeiters • Dies in 1727 1726 engraving

30. Edmund Halley (1656-1742) • HALL ee, not Hail ee! • English Astronomer • Proposed using transits of Mercury and Venus to determine the distance of the Sun and therefore the scale of the solar system using Kepler's third law • Suggested that Kepler’s 3rd Law implied an inverse square relation • Predicted the return of the 1705 comet • 1305, 1380, 1456,1531, 1607, 1682 • Period?

31. Bill Haley and the Comets

32. Christian Huygens (1629 - 1695) • Dutch Physicist • Proponent of wave theory of light • Argued with Newton over this • Discoverer of Titan • Lander named after him • Correctly identified Saturn’s ‘ears’ as rings

33. Comparison of observations of Saturn by Galileo, Scheiner, Hevelius and others from 1616-1655,from Huygens' Saturnian System (1659)

35. Giovanni Cassini (1625 - 1712) • Mathematician and Astronomer • Astronomer at the Panzano Observatory • Director of the Paris Observatory • Viewed a ‘gap’ in Saturn’s ring system • correctly proposed that the rings were composed of large numbers of tiny satellites each orbiting the planet. • But he was a geocentrist!

36. Other Accomplishments • 1664: measured the period of rotation of Jupiter on its axis, discovered the bands and spots on the planet, and saw that the planet was flattened at its poles • 1666: measured the period of rotation of Mars on its axis, getting a value within three minutes of the correct one, and observed surface features • He was the first to observe four of Saturn's moons: Iapetus (1671), Rhea (1672), Tethys (1684), and Dione (1684) • Made successful measurements of longitude by the method suggested by Galileo

37. The Longitude Problem • Age of discovery: needed for navigation • Latitude easy • North Star • Equal spacing • Longitude more difficult • The lines of longitude fan out from one pole to a maximum at the equator then reconverge

38. A clock is needed • 1530Gemma Frisius of Antwerp proposed use of portable mechanical clock • Won’t work on a rocking ship • 1636Galileo proposes using mechanical clock and moons of Jupiter to determine longitude • Off world clock versus local time • 1676Greenwich Observatory founded • 1714Queen Anne establishes the longitude prize -- £20,000!!

39. And the winner is: • John Harrison 1693-1776 • working class carpenter • Build dual spring pendulum H1

40. H2 and H3

41. H4 1765 • Accurate to 40 seconds/day, 3X better than the prize required • Prize committee baulked at £20,000, offered £10,000 for H1-H4 • Both sides stubborn but Harrison finally agreed • Actually got £8750 in 1773 for H1-H5

42. Prime Meridian established through Greenwich Observatory • GMT • As important to Astronomy as to navigation • 118W, 34N: home!

43. Time Zones

44. Coincidence??? Capt. James Cook Capt. James Kirk Used the H4 chronometer on his 2nd and 3rd voyages of discovery Boldly voyaged where no-one had gone before

45. Eventual Acceptance: Laplace 1796 • Astronomy considered in its entirety is the finest monument of the human mind, the noblest essay of its intelligence. Seduced by the illusions of the senses and of self-pride, for a long time man considered himself as the centre of the movement of the stars; his vainglory has been punished by the terrors which its own ideas have inspired. At last the efforts of several centuries brushed aside the veil which concealed the system of the world…

46. continued • …We discover ourselves upon a planet, itself almost imperceptible in the vast extent of our solar system, which in turn is only an insensible point in the immensity of space. The sublime results to which this discovery has led should suffice to console us for our extreme littleness, and the rank which it assigns to the earth.

47. Eventual Acceptance: Goethe 1810 • “But among all the discoveries and new convictions nothing may have produced greater effect on the human spirit than the doctrine of Copernicus. The world had scarcely been recognized as round and complete in itself when it was expected to relinquish the enormous privilege of being the center of the universe. A greater demand may never have been addressed to mankind. For think of all the things that went up in smoke as a result of accepting this: a second Paradise, a world of innocence, poetry and piety, the testimony of the senses, the conviction of a poetic-religious faith: it is no wonder that people did not want to give up all of this, and that they opposed such a doctrine in every way--a doctrine that justified those who accepted it in, and summoned them to a previously unknown, indeed unimagined freedom of thought and largeness of views”