Johannes Kepler

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Johannes Kepler

Johannes Kepler (December 27, 1571 – November 15, 1630),[1] a Protestant in Germany, was a brilliant mathematician, astronomer, astrologer,[2] and devout Christian who cited God many times in all of his writings. He felt it was his Christian duty to understand the creation of God and the universe, and that God had used a mathematical plan for the universe's design.[1] He also felt that man, being in the image of God, was fully capable of understanding the universe. Like Plato and Pythagoras, Kepler felt that God must have created the universe according to a mathematical plan (see Cause of the universe).

Life and career

Kepler was born in Weil der Stadt, Württemberg, in what was then known as the Holy Roman Empire, and more particularly in that part of it now known as Germany.[1][3][4] He observed his first comet at the age of six and his first eclipse of the Moon at the age of eight or nine.[1] Kepler overcame an enormous obstacle to become a great scientist, as he suffered from an attack of smallpox when he was only four years old. The disease left him with poor eyesight and crippled hands for the rest of his life.

Kepler entered the Lutheran seminary at Adelberg in 1584,[3] and in 1589 he won a scholarship to study theology at the University of Tübingen.[4]

In that era, no serious thinker sought to connect astronomy, a "mathematical" discipline, with physics. But Kepler sought out his first passion to discover the planets' paths, instead of settling for what was assumed. He also came under the influence of Michael Maestlin, who was one of the first astronomers to realize, as had Nicolaus Copernicus, that the Earth and the other planets revolved around the Sun. Maestlin taught heliocentrism only to graduate students, of whom Kepler was one.

Scientists of that time were often opinionated and prone to risk-taking in their theories, and Kepler was no exception. He sacrificed his religious reputation by questioning the "science" of the time, which later forced him to be cut off from orthodox Lutheranism. Although the loss was great, Kepler was able to become a mathematician and teacher in Graz, Austria, in 1594.[1][3] While at Graz, Kepler wrote his famous Mysterium Cosmographicum, the first forthright and public defense of Copernican heliocentrism.[4]

In 1600, Kepler left his job at Graz on account of the Counter Reformation. Unwilling either to convert to Catholicism or to sign the Lutheran Formula of Concord, he decided to leave Graz and travel to Prague.[3][4] There he became the assistant to Tycho Brahe, court mathematician to Emperor Rudolf II.[1] Tycho was also making observations on the orbit of the planets. In 1601, Tycho died, and Kepler was named Imperial Mathematician in his place,[4] the highest ranking in Europe at the time.[3] After reading and studying the data that Tycho had developed and researched, Kepler was able to resolve a nagging problem concerning the motion of Mars, and in particular its apparent retrograde motion in relation to the Earth. Kepler went on to calculate Mars' orbit—as an ellipse, not a circle.

Kepler remained as Imperial Mathematician until 1612, when Rudolf II was deposed.[3] In the next year (1613) he accepted a teaching position in Linz, the last semi-permanent position he ever held. He held this job until 1626, when the pressures of the Thirty Years' War forced him to leave. Now out of a job and with no salary, he tried in vain to seek employment and to sue for back payment of his salary as Imperial Mathematician.[3] He died in 1630, at Regensburg.[3][4]

Kepler's contributions to astronomy

From this material Kepler formulated his three Laws of planetary motion, his best-known contribution to astronomy. Central to these laws is the insight that celestial bodies travel in elliptical orbits. What might not be widely appreciated is that he endeavored to link astronomy with physics.[1] Kepler published his first exposition of his laws, Astronomia Nova, in 1609. Kepler's insights would later help Sir Isaac Newton formulate his law of gravity.

Very few of his fellow scientists appreciated the link between astronomy and physics. Galileo Galilei, discoverer of the four dwarf planet sized moons of Jupiter, virtually ignored Kepler, as did René Descartes and even his old mentor Michael Maestlin.[1] But Kepler did not ignore Galileo. He published a lengthy letter of support for Galileo in 1610, after Galileo had published his findings of the Jovian moons, and in 1611 he published his own detailed observations of those same satellites. He made those observations, accurate to within one-tenth of a degree, once he acquired a suitable telescope.[3]

Kepler's other contributions

In 1613, while at Linz, Kepler published his own calculation of the exact year of the birth of Jesus Christ. He it was who first concluded that the Julian-Gregorian calendar systems were off by four years, and that Jesus was born in 4 BC (Julian calendar), not AD 1.[5] Other tomes to his credit include Harmonices Mundi (1619, a defense of his Third Law of Planetary Motion) and Epitome Astronomiae (1621, a systematic defense of heliocentrism in seven volumes).[4] His last work was the Rudolphine Tables (named for Rudolf II), a completion of Tycho Brahe's work. In that work he used logarithms, which he developed, to calculate predicted positions of all the planets known to that time. Those tables correctly predicted two solar transits of Mercury and Venus, events that occurred after his death but on the dates he predicted.[4]

Kepler's insights

Kepler wrote in book five of his work, Harmonices Mundi:

O, Almighty God, I am thinking Thy thoughts after Thee! ... The book is written, to be read either now or by posterity, I care not which. It may be well to wait a century for a reader, as God has waited six thousand years for an observer.

Kepler compared the celestial orbits of the planets with polyphonic harmonies in music. He wrote:

Holy Father, keep us safe in the concord of our love for one another, that we may be one just as Thou art with Thy Son, Our Lord, and with the Holy Ghost, and just as through the sweetest bonds of harmonies Thou hast made all Thy works one; and that from the bringing of Thy people into concord, the body of Thy Church may be built up in the Earth, as Thou didst erect the heavens themselves out of harmonies.

External links


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Dao, Christine. "Man of Science, Man of God: Johann Kepler." Institute for Creation Research. Accessed March 2, 2008.
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Van Helden, Al. "Johannes Kepler (1571-1630)." The Galileo Project, Rice University, 1995. Accessed March 2, 2008.
  4. 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 "Johannes Kepler: His Life, His Laws, and Times." NASA. Accessed March 2, 2008.
  5. James Ussher might have used those calculations in his Annals to fix the date of Christ's birth and the Crucifixion.