Johann kepler was born nera Stuttgart in 1571 and educated at the University
of Tubingen, with the original intention of becoming a Lutheran minister. His
deep interest in astronomy led him to change his plans, and in 1594, when in his
early twenties, he accepted a lectureship at the University of Gratz in Austria.
In 1599, he became assistant to the famous but quarrelsome Danish-Swedish
astronomer Tycho Bhortly, who had moved to Prague as court astuonomer to
¥±. Shortly after, in 160-1, Brahe suddenly died, and
inhirited both his master's position and his vast and very accurate
astronomical data on the motion of the planets. He made
hundreds of fruitless attempts and performed reams and reams of calculations,
laboring with undiminished zealand patience for twenty-one years. Finally, in
1619, his third law, of planetary motion.
These laws of planetary motion are landmarks in the history fo astronomy
and mathimatcs, for in the effort to justify them isaac Newton was led to
create modern celestial mechanics. The three laws are:
¥°. The planets move abort the sun in
elliptical orbits with
the sun at one focus.
¥±. The radius vector joining a planel to
the sun sweeps over
equal areas in equal
intervals of time.
¥². The square of the time of one compete revolution of a planet
aboutits orbit is proportional to the cube of the orbit'ssemimajor
The empirical discobery of these laws from Brahe's mass of data constitutes
one of the most remarkable inductions ever made in science.
kepler's work is often a blend of mystical and highly fanciful speculation,
combined with a truly deep grasp of scientific truths. It is sad that his personal
life was made almost unendurable by a succession of worldly misfortunes. An
infection from smallpox when he was but four years old left his eyesight much
impaired. In addition to his general lifelong weakness, he spent a joyless youth,
his marriage was a constant source of unhappiness; his favorite child died of
smallpox; his wife went mad and died; he was expelled from his lectureship at
the University of Gratz when that city fell to the Catholics; his mother was
charged and imprisoned for witchcraft, and, for himself wery narrowly escaped
condemnation of heterodoxy; and his stipend was always in arrears. One report
says that his second marriage was even less fortunate than the first, although he
took the precaution to analyze carefully the merits and demerits of eleven girls
before choosing the wrong one. He was forced to augment his income by
casting horscopes, and in 1630 he died of a fever while on a journey to obtain
some of his long overdue sasry.