Kepler's laws of planetary motion
- Author:
- Roman Hašek
The motion of planets is describedby the three Kepler’s laws, which belong to the usual secondary school curriculum.
Johannes Kepler (1571–1630), German mathematician and astronomer, whose life was closely connected to Graz and Linz in Austria, and Praha in Bohemia, published the three laws over a period of time in two books.
He based his findings on observations of the Danish astronomer Tycho Brahe (1546–1601).
First, in 1609 in Astronomia nova, Kepler published two statements that are known as his 1^{st }and 2^{nd} laws of planetary motion.
- Orbits of all the planets are ellipses with the Sun at one focus (Kepler’s 1^{st} law, the law of ellipses).
- A line segment from the Sun to a planet sweeps out equal areas in equal time (Kepler’s 2^{nd} law, the law of equal areas).
- The orbital period of a planet is proportional to the three-halves power of the size of the semi–major axis of its orbit (Kepler’s 3^{rd} law, the law of harmonies).