Kepler (1571-1630)
Kepler is most famous for his 3 laws of planetary motion.
Law 1
The orbit of a planet / comet about the Sun is an ellipse with the Sun at one
focus
Law 2
A line joining a planet to the Sun sweeps out equal areas in equal time
intervals
Law 3
The squares of the periods of the planets are proportional to the cubes of their
mean distance from the Sun
| Planet | Period T (yr) | Mean Distance R (AU) | T2 | R3 | T2/R3 |
|---|---|---|---|---|---|
| Mercury | 0.24 | 0.39 | 0.06 | 0.06 | 1 |
| Venus | 0.62 | 0.72 | 0.39 | 0.37 | 1 |
| Earth | 1.00 | 1.00 | 1.00 | 1.00 | 1 |
| Mars | 1.88 | 1.52 | 3.53 | 3.51 | 1 |
| Jupiter | 11.9 | 5.20 | 142 | 141 | 1 |
| Saturn | 29.5 | 9.54 | 870 | 868 | 1 |
You can draw a circle with a loop of string, a nail and a pencil. You can draw an ellipse by using two nails. See how the shape of the ellipse changes when you change the distance between the nails.
For more information http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Kepler.html