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Kepler’s great breakthrough was his
calculation of the actual form of the
planetary orbits, but the physics
behind his three laws did not
seem to concern him. Rather, he
suggested that Mars was carried
on its orbit by an angel in a chariot,
or swept along by some magnetic
influence emanating from the sun.
The idea that the movements were
due to a gravitational force only
arrived with the ideas of Isaac
Newton some 70 years later.
Wider contributions
Kepler also made important
advances in the study of optics,
and his 1604 book Astronomiae
Pars Optica is regarded as the
pioneer tome in the subject.
Galileo’s telescope interested him
greatly and he even suggested
an improved design using convex
lenses for both the objective and
the magnifying eyepiece. He
wrote, too, about the supernova
that was first seen in October 1604,
today commonly called Kepler’s
supernova. Following Tycho, Kepler
realized that the heavens could
change, contradicting Aristotle’s
idea of a “fixed cosmos.” A recent
planetary conjunction coupled
with this new star led him to
speculate about the Biblical “Star
of Bethlehem.” Kepler’s fervent
imagination also produced the
book Somnium, in which he
discusses space travel to the
moon and the lunar geography
a visitor might expect on arrival.
Many regard this as the first work
of science fiction.
Kepler’s most influential
publication, however, was a
textbook on astronomy called
Epitome Astronomiae Copernicanae,
and this became the most widely
used astronomical work between
1630 and 1650. He ensured thatTHE TELESCOPE REVOLUTION
In Harmonices Mundi, Kepler
experimented with regular shapes
to unlock the secrets of the cosmos.
He linked these shapes with harmonics
to suggest a “music of the spheres.”the Rudolphine Tables (named
after Emperor Rudolf, his patron
in Prague) were eventually
published, and these tables of
predicted planetary positions
helped him greatly with the well-
paid calendars that he published
between 1617 and 1624. The
accuracy of his tables, proven
over a few decades, also did much
to encourage the acceptance of
both the Copernican sun-centered
solar system and Kepler’s own
three laws. ■Kepler was convinced that
God created the world in
accordance with the principle
of perfect numbers, so that the
underlying mathematical
harmony ... is the real and
discoverable cause of the
planetary motion.
William Dampier
Science historian