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1. Tycho Brahe (1546-1601) 1
2. Brahes Quadrant 2
3. Brahes Observations Observed Supernovae ? changes in heavens 3
4. Brahes Observations (cont.) 4
5. Making sense of it all 5
6. Johannes Kepler (1571-1630) 6
7. Kepler as lecturer 7
8. Mysterium Cosmographicum (1595) Tried to the distances of the planets from the Sun in the Copernican system to the five perfect solids of the neo-platonists
He pursued this model till his death but it never worked satisfactorily
8
9. Because of talent as a mathematician: He was invited by Tycho Brahe to become his assistant in 1600
Task: calculate the orbit of Mars Tycho's observations
He bet his fellow workers that he could solve the problem in 8 days 9
10. Tychos Tables 10
11. 8 days ends up 8+ years He first tried a heliocentric model with circular orbits but Sun not at the center
900 pages of calculations
Mars orbit fit Brahes data to within 2 of celestial arc (= 2/60th of a degree)
Vast improvement on Copernicus 11
12. Failure New observations ? errors of up to 8
Rejected his model: if I had believed we could ignore these 8, I would have patched up my hypothesis accordingly. But since it was not permissible to ignore them, these 8 point the road to a complete reformation of astronomy. 12
13. and new models He next tried a model based on oval orbits spent 3 years on them
Wrote in 1603 if only the shape were a perfect ellipse all the answers could be found in Archimedes and Apollonius works
Wrote 18 months later that the truth must lie between a circle and an oval, just as if the Martian orbit were a perfect ellipse. 13
14. It turned out the orbit of Mars 14
15. More than 8 years of work He later wrote I thought and searched, until I nearly went mad, for a reason why the planet preferred an elliptical orbit . . . Ah, what a foolish bird I have been. 15
16. Small eccentricity is the problem 16
17. Astronomia Nova(1609) 17
18. Harmonices Mundi (1619) 18
19. Tabulae Rudolphinae (1625) Astronomical tables which reduced errors in planetary position to < 1% 19
20. Keplers First Law 20
21. Keplers Second Law 21
22. A bit like Ptolemys Equant Circle 22
23. Keplers Third Law 23
24. Keplers Third Law 24
25. Keplers Laws are: 25
26. If there are no crystalline spheres, what moves the planets? 26
27. A web site about Keplers Laws 27