New Astronomy (1609)
Kepler spent almost 10 years trying to determine the orbit of Mars from Tycho’s data.
Using compounded circles, his best effort got agreement within 8’ of arc (1/4 of moon’s diameter)….. much better than any previous solution.. BUT Tycho’s data claimed 4’ of arc accuracy.
Solution: ABANDON PARADIGM OF UNIFORM CIRCULAR MOTION!!
Two Changes:
- PATH: elipses instead of circles
- SPEED: not uniform - varies with the time of year (departure from Platonic ideal of circles)