Mysterium cosmographicum (1596)
The Cosmographic Mystery; explained the spacing of the six known planets by nesting the five Platonic solids
Science · Maths, astronomy, medicine & more
Johannes Kepler
1571–1630 · German
Astronomy — planetary motion
Johannes Kepler, a German mathematician and astronomer, used Tycho Brahe's precise observations of Mars to show that planets move in ellipses, not circles. His three laws of planetary motion, set out in Astronomia nova (1609) and Harmonices mundi (1619), turned the Copernican system into an accurate physical model and paved the way for Newton's theory of gravitation. He served as Imperial Mathematician to Emperor Rudolf II in Prague.
How to spot them
- ▸Three laws of planetary motion: elliptical orbits, equal areas in equal times, and the square of the period proportional to the cube of the distance
- ▸Assistant to Tycho Brahe in Prague; Imperial Mathematician to Rudolf II; the Rudolphine Tables
- ▸Nested Platonic solids in Mysterium cosmographicum; the 'music of the spheres' in Harmonices mundi
- ▸His mother Katharina was tried for witchcraft
- ▸NASA's planet-hunting space telescope; the supernova of 1604
Key discoveries & works
Astronomia nova (1609)
The New Astronomy; from Tycho's Mars data, the first two laws: elliptical orbits and equal areas in equal times
Harmonices mundi (1619)
The Harmony of the World; contains the third (harmonic) law linking orbital period and distance
Rudolphine Tables (1627)
Planetary tables named after Emperor Rudolf II, far more accurate than any before them
Somnium (1634 (posthumous))
The Dream; a fictional journey to the Moon often called one of the first works of science fiction
Strena seu de nive sexangula (On the Six-Cornered Snowflake) (1611)
New Year's gift treatise on why snowflakes are six-sided; includes the sphere-packing conjecture
Observation of the supernova of 1604 (1604)
The last supernova seen with the naked eye in the Milky Way, SN 1604, now named after him
Key ideas
- First law: each planet moves in an ellipse with the Sun at one focus
- Second law: a line from the Sun to a planet sweeps out equal areas in equal times
- Third law: the square of a planet's orbital period is proportional to the cube of its mean distance from the Sun
- Sought physical causes for planetary motion, suggesting a force from the Sun, rather than pure geometry
- The Kepler conjecture: no packing of equal spheres is denser than the face-centred cubic arrangement (proved by Thomas Hales)
Quick-fire facts
- •Born 27 December 1571 in Weil der Stadt, Württemberg; died 15 November 1630 in Regensburg
- •Educated at the University of Tübingen, where Michael Maestlin taught him the Copernican system
- •Joined Tycho Brahe in Prague in 1600 and succeeded him as Imperial Mathematician after Tycho's death in 1601
- •His long struggle to fit the orbit of Mars was later described as his 'war with Mars'
- •His mother Katharina was charged with witchcraft; Kepler conducted her defence and she was released in 1621
- •NASA's Kepler space telescope (launched 2009) discovered thousands of exoplanets
- •Paul Hindemith wrote an opera about him, Die Harmonie der Welt
Drill it — 9 cards
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Sources
- MacTutor History of Mathematics, University of St Andrews — Johannes Kepler
- Arthur Koestler — The Sleepwalkers