From: JASA 37 (June 1985): 93-96.
Johannes Kepler (1571-1630) was a rare and strange man whose life was fraught with vicissitudes stemming from the Diet of Augsburg (155 5) with its principle "cuius regio, eius religio" to the devastating Thirty Years War (1618-1648). He was born of Lutheran parents (father a soldier, mother daughter of an innkeeper) in Weil der Stadt, Wfirttemberg. At seven he was sent to a cloister Latin school and at thirteen to a seminary, from which he received a B.A. Two years later he was awarded an M.A. from the protestant University of TUbingen, which he had entered at eighteen to become a Lutheran priest. In the middle of the third year of his subsequent theological preparation the faculty recommended him to be teacher of mathematics and astronomy at the protestant seminary in Graz, Austria, where he was also appointed District Mathematician. (He married at twenty-six.) At twenty-eight he met the Danish astronomer Tycho Brahe (1546-1601) at Prague. Not being a Catholic, he was banished the following year. At thirty he began collaborating with Brahe on the Rudolphine Tables. In that very year, however, Brahe died; Rudolph 11 appointed Kepler to succeed him as Imperial Mathematician. Only his wife's income saved him from the embarassment of uncertain salary payments. Upon the Emperor's forced abdication in 1612 and his own refusal to become a Catholic, he had to seek employment elsewhere again, this time as District Mathematician in Linz. (His wife having died, he remarried-a happier venture.) Here, too, war developed so that at fifty-rive he had to seek protection from Gen. Albrecht Wallenstein, who supported him in Sagan, Poland. On a journey in 1630 he died at Regensburg. His burial place and the entire church graveyard were destroyed shortly by war. His second wife died at forty-seven virtually in poverty.
Kepler had many intellectual interests and wide knowledge. His industry and perseverance were prodigious, e.g., he was not satisfied with an 8' minute discrepancy between his calculated result of Mars and the careful observation by Brahe. He had an inventive genius, e.g., his insertion of Euclid's five perfect solids within the spheres of the six orbiting planets (cf. the 1596 "Mysterium Cosmographicum"; he himself noted two of the four possible star polyhedra). His outstanding characteristic, however, was his integrity resulting in sincere and frank behaviour. He was conscientious; agreeing with the new Gregorian calendar (1582), he did not side with the protestant opposition, which lasted until about 1700. Despite his personal political problems he never resorted to religious agitation; he was always urging peace. Himself modest, he recommended that jealous observers share their observations of an eclipse. He had a noble spirit; he was deeply religious.
Kepler's fascination for the "heavens in their mysterious beauty" began with the comet his mother pointed out when he was six and with the eclipse his father showed him at nine. He became a careful observer (despite weak eyes), an industrious computer, and an imaginative theorist, seeking symmetries and analogies. It is not surprising that he noted the (super)nova in Ophuichus (1604) (cf. Brahe's [super) nova in Cassiopeia 5721). It was not until 1627 that he completed the Rudolphine Tables. Meanwhile he used Brahe's excellent data to seek simple planetary orbits. Regarding the earth's motion itself as nonuniform he was led to the fact that the radius vector connecting the sun and a planet sweeps out equal areas in equal times and, indeed, that the orbit is an ellipse. These two laws were announced in his "Astronomia Nova" (1609). No more is one concerned with kinematics, circular motions, epicycles, fictional centers, and oscillations; the sun at one focus, is the origin of an attractive force (magnetic?)-the beginning of celestial mechanics. Two years later in his "Dioptrice" he laid the foundations of modern geometrical optics (the correct refraction law was not discovered until ten years later by Snell). It was not until 1619 that he was able to announce the third Kepler law, which relates a planet's period T to its mean distance r from the sun (T' o, P), in the "Harmonices Mundi. "
A Platonist, Kepler was a mathematical mystic. He believed that "everything in nature is arranged according to measure and number." He was convinced that "the geometrical natures of things have provided the Creator the model for decorating the whole world." (He investigated the regularity of the six angles of a snowflake in "Strena" (1611),) His axiom was that "nothing in the world was created by God without a plan"; he sought it diligently.
Kepler's official duties included preparation of ephemerides and calendars, involving weather predictions and astrological notes. He was the first to place the birth of Jesus at 4 B.C. He himself kept weather data for twenty years. As for any influences of the stars, he exercised restraint and caution-he recognized their general psychic effects, but avoided specific predictions. He seized the opportunity to give moral admonitions, to urge peaceful practices.
Kepler wrote occasional papers on theology, but he never claimed to be a theologian. He regarded himself as a layman who was a mathematician, a (natural) philosopher, a historian. And yet, he was probably the scientist who par excellence regarded science and religion as different aspects of an integrated world-not an artificial, academic bifurcation. The goal of science, he believed, is to bring man to God; the principle of his scientific work is praise of God. "We astronomers are priests of the highest God in regard to the book of nature." "God is the beginning and end of scientific research and striving"-the keynote of his thought, the basis of his purpose, the "life-giving soil of his feeling." For him, "geometry is unique and eternal, a reflection of the mind of God. That mankind shows in it is because man is an image of God."
Kepler regarded the Copernican theory as literally
not a convenient fiction. With respect to questionable Biblical passages (e.g. Josh. 10: 12, Ps. 104, Job 34), he noted, "It
is not the purpose of the Holy Scriptures to instruct men in
Despite his exemplary life, he was denied communion by
his own Lutheran church, first at Graz, finally by Tffbingen
in answer to his formal petition. Although he subscribed
wholeheartedly to the Augsburg Confession (15 30), he could
not quite endorse the Book of Concord (1580) because of its
doctrine of the omnipresence of Christ (e.g., in the sacrament). He preferred the Calvinistic emphasis upon remembrance, but could not accept its complementary insistence
upon predestination. He regarded himself as a catholic
(including Lutherans and Calvinists, as well as Roman
Catholics), but he could not agree with the Papacy (e.g., it's idolatry, saints, et al.).
Kepler's scientific writings are interspersed with pertinent religious comments. The "Harmonices," his favorite work, begins and ends with an appropriate prayer, (it contains also explanations about Jesus Christ). The conclusion begins, "0 Thou, who by the light of nature increases in us the desire for the light of Thy mercy in order to be led by this to Thy glory, to Thee I offer thanks, Creator, God, because Thou hast given me pleasure in what Thou hast created and I rejoice in Thy handiwork." His dying words were: "Only the merits of our saviour Jesus Christ. It is in Him, as I steadfastly testify, that there rest all my retreat, all my consolation, all my hope."