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Sunday, 25 October 2015

Johannes Kepler

German mathematician and astronomer Johannes Kepler was born on December 27, 1571, at the Free Imperial City of Weil der Stadt (50 miles west of Stuttgart). Johannes' father, Heinrich Kepler, earned a precarious living as a mercenary, and he left the family when Johannes was five years old.. His mother Katharina Guldenmann, an inn-keeper's daughter, was a healer and herbalist.

Johannes was introduced to astronomy at an early age, and observed at the age of six the Great Comet of 1577.

Kepler attended Tübinger Stift at the University of Tübingen. There, he studied philosophy and theology. He proved himself to be a superb mathematician and earned a reputation as a skillful astrologer, casting horoscopes for fellow students.

Brought up in the Protestant faith, Kepler had desired to become a minister. However, near the end of his studies he was recommended for a position as teacher of mathematics and astronomy at the Protestant school in Graz. Kepler accepted the position in April 1594, at the age of 23.


Kepler first met the Danish astronomer Tycho Brahe on February 4, 1600, at Benátky nad Jizerou (55 miles from Prague), the site where Brahe's new observatory was being constructed. Over the next two months he stayed as a guest, analyzing some of Tycho's observations of Mars.

Through most of 1601, Kepler was supported directly by Tycho, who assigned him to analyzing planetary observations.

Monument of Tycho Brahe and Johannes Kepler in Prague

After Tycho's unexpected death on October 24, 1601, Kepler was appointed his successor as imperial mathematician to Emperor Rudolf II, with the responsibility to complete his unfinished work. His analysis of Tycho's observations of the planets led him to discover Kepler's laws.



Kepler's three laws of planetary motion provided evidence that the planets, including the Earth, orbit the Sun in an oval shape. The German astronomer showed that the orbits of the planets are elliptical rather than circular, and that a planet's speed varies at different stages of its orbit. Moreover, planetary motion follows music's template. For example, the ratio between Jupiter's maximum and Mars' minimum speed corresponds to a minor third; that between Earth and Venus to a minor sixth.

Kepler's first two laws were published in Astronomia nova (New Astronomy) in 1609. His third law, which he discovered on March 8, 1618, was outlined in Harmonice Mundi (Harmony of the Worlds) ten years later.

Geometrical harmonies in the perfect solids from Harmonices Mundi 

On October 17, 1604, Johannes Kepler observed an exceptionally bright star, now known as Kepler's Supernova, which had suddenly appeared in the constellation Ophiuchus. while working at the imperial court in Prague for Emperor Rudolf II. Kepler tracked the object for an entire year and in 1606 wrote a book on the subject, entitled De Stella nova in pede Serpentarii ("On the new star in Ophiuchus's foot".  Kepler's Supernova is the most recent supernova to have been unquestionably observed by the naked eye in the Milky Way.


In the first months of 1610, Kepler's contemporary, Galileo Galilei, using his powerful new telescope, discovered four satellites orbiting Jupiter. After hearing of Galileo's telescopic discoveries, Kepler started his own theoretical and experimental investigation of telescopic optics using a telescope borrowed from Duke Ernest of Cologne. The resulting manuscript, which helped to legitimize the telescopic discoveries of Galileo, was published as Dioptrice in 1611.

Kepler's Protestant faith was not affected  by his astronomical findings as he believed that the source of all power and light, the Sun is the very image of God. Kepler asserted that his discoveries "may well wait a century for a reader, as God has waited 6,000 years for an observer."

When Kepler was at the very height of his scientific career, his mother, Katharina, was accused of witchcraft. Kepler abandoned everything to defend her against the claims of witchcraft--over a period of six years--saving her from sure execution at the stake.

In 1628, following the military successes of the Emperor Ferdinand's armies under General Wallenstein during the Thirty Years War, Kepler was appointed as an official adviser to Wallenstein. He provided astronomical calculations for Wallenstein's astrologers and occasionally wrote horoscopes himself.

Kepler died in the South East German city of Regensburg on November 15, 1630. His burial site there was lost after the Swedish army destroyed the churchyard. Only Kepler's self-authored poetic epitaph survived the times:

I measured the skies, now the shadows I measure
Skybound was the mind, earthbound the body rests.

Source The Observer Book of Space

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