Astronomer and mathematician — Johannes Kepler (Weil der Stadt 1571 – Regensburg 1630) was a German astronomer and mathematician, a key figure of the scientific revolution. A convinced Copernican and deeply religious, he sought throughout his life the mathematical harmony of the cosmos. Having become Tycho Brahe’s assistant and then successor in Prague, he inherited Brahe’s extremely precise observations, particularly those of Mars, and from them derived the three laws of planetary motion: orbits are ellipses with the Sun at one focus, definitively superseding the perfect circles of tradition. These laws, empirical but exact, later gave Newton the basis for the law of universal gravitation. Kepler also made important contributions to optics, lens theory and the mathematics of solids.
Trivia
Between 1615 and 1621 he had to defend his mother Katharina in a long trial, as she was accused of witchcraft and risked torture; thanks partly to his defence, she was eventually acquitted.
Theories and contributions
- First law (of orbits) — Every planet describes an elliptical orbit with the Sun at one of the two foci.
- Second law (of areas) — The line joining planet and Sun sweeps out equal areas in equal times: .
- Third law (of periods) — The square of the period is proportional to the cube of the semi-major axis: .
Featured in chapters
Linked atoms
6 linked atoms.
08 Gravitazione universale
- Conservation of angular momentum and Kepler’s second law
- Kepler’s laws
- Satellites and circular orbits
- From Kepler to Newton: universal gravity