The Unlocking of the Solar System

1. The Unlocking of the Solar System Prepared for CVCA Physics by Dick Heckathorn 2 December 2K + 4

2. 13Copernicus 27 Brahe 38 Kepler 86 Biblical 95 Satellite Overhead 98 Galileo 128 Newton 131 Side Bar 139 Back to Newton 158 Period of Moon 167 Cavendish 176 Determine g on planets 174 Useful Equations 176 Mass of Sun 181 Earth Moon Orbit Materials 51 – cardboard, paper, tacks string 55 – Handout – Data Sheet 56 – Cardboard models 118 – Video Galileo 147 – Video Apple and Moon 183 – Earth Moon Apparatus

3. The Greeks Concerned with observing and measuring phenomena and being able to express results in the language of number and geometry.

4. The Greeks Postulate: Heavenly bodies must execute “perfect” circular motions.

5. Plato427-317 BC The circle was believed to be the most perfect of all curves and hence alone worthy of describing celestial motions.

6. Plato “The stars seem to move in perfect circular paths around the earth, but the planets seem to trace irregular paths.”

7. Plato A Challenge “Determine what uniform and ordered (circular) motions must be assumed for each of the planets to account for its apparently irregular yearly paths.”

8. Eudoxus(Plato’s Pupil) Used collection of moving spheres, each with its center at the earth. Good approximation In one such system it took 13 spheres for Mercury’s alone.

10. Ptolemy of Alexander2nd Century AD Used circles moving on other circles

11. Ptolemaic Model

12. Alphonso X, King of Castilein 1200 “If I had been consulted at the creation, I would have made the world on a simpler and better plan.”

14. Copernicus (1473-1543) A humble compassionate man who was not only a most remarkable astronomer and mathematician, but also a churchman, administrator, diplomat and physician.

15. Copernicus There are considerable discrepancies between observation and prediction of planetary positions. Even the exact length of the year is in doubt.

16. Copernicus “The Ptolemaic system was too complex!” “The truth might be simpler.”

17. Copernicus “I too might well be allowed to try whether sounder demonstrations of the revolutions of the heavenly bodies might be discovered by supposing some motion of the earth.”

18. Copernicus “I will assume the earth rotates.” “This then will describe the motion of the fixed stars.”

19. Copernicus Any type of celestial motion other than uniform circular motion was “obviously” impossible. carry over from Plato

20. Copernicus “If the sun, rather than the earth was chosen as the center of planetary motion, the orbits of the planets could be greatly simplified.”

21. Copernicus Using calculations he proved that the motion of celestial objects as then known could be represented by a combination of uniform circular motions in a sun-centered system.

23. Copernicus To believe this was to discard the entire picture of the universe that had been developed from the time of Aristotle.

24. Copernicus Whether or not the earth moves was a very serious question to ponder.

25. The Roman Catholic Church Denounced the Copernican theory as “false and altogether opposed to the Holy Scriptures.”

26. Some Questions for Copernicus If the earth does move, what pushes it? Why is the motion not felt? Why do the stones fall to the earth if it is not the center of the universe?

27. Tycho Brahe

28. Tycho Brahe (1546-1601) Danish Did not agree with Copernicus. “The Sun goes around the earth, the planets go around the sun.”

30. Tycho Brahe 1576 (30 years old) on Island of Hveen Built observatory

34. Tycho Brahe Observed and Recorded for 20 years Cataloged 777 stars Observations to within 10 seconds of arc.

35. Tycho Brahe (1546-1601) Had no telescope Galileo (1564-1642) Refined one to observe the heavens

36. Tycho Brahe to Prague in 1597

37. Tycho Brahe 1600 Kepler became his assistant

39. Johanas Kepler 5. Johanas Kepler (1571-1630) 4. Galileo Galilei (1564-1642) 3. Tycho Brahe (1546-1601) 2. Copernicus (1473-1543) 1. Plato (427-317 BC)

40. Johanas Kepler Was a Copernican. Believed in heliocentric model. Supported himself as an astrologer.

41. Johanas Kepler “The clue to God’s mind was in geometric order and mathematical relationships, expressed in the features of the simple heliocentric scheme.”

42. Johanas Kepler Desire: to use geometry and mathematics to explain the number, distance and motion of Mars.

43. Johanas Kepler “I brooded with the whole energy of my mind on this subject.”

44. Johanas Kepler Tried to fit data of Mar’s position on a circular orbit. After four years he was unable to do it. Data was outside orbit by 8 minutes of arc.

45. Johanas Kepler With integrity, he could not allow himself to hide this difference which to him was significant as he know of Brahe passion for accuracy.

46. Johanas Kepler As he continued to analyze the data, he remembered another simple type of figure, the ellipse, that had been known since the 3rd century B.C.

47. Johanas Kepler This time, the data for the position of Mars as determined by Brahe fit the elliptical path.

48. Johanas Kepler Law 1 - Law of Elliptical Paths Mars (and all the other planets) move in an elliptical path, with the sun at one focus of their ellipse. Mercury, Venus, Earth, Mars, Jupiter, Saturn

49. The Ellipse What are it’s properties? How does one draw one? *** Do it. ***

50. The Ellipse How much does the ellipse of the orbits of the planets differ from a circle? By its eccentricity.