Johannes Kepler

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Johannes Kepler (1571-1630)

Johannes Kepler (born::December 27, 1571 - died::November 15, 1630)[1] was a German mathematician, astronomer and astrologer and the first scientist to accurately observe and explain planetary motion and natural laws. He was a man of great brilliance that discovered that our sun rotates about its axis and that ocean tides are caused by the moon. His knowledge and discoveries contribute to our vast knowledge of the sun and moon, the stars, and positions of our planets.

Life and career

Kepler was born in Weil der Stadt, Württemburg, in what was then known as the Holy Roman Empire, and more particularly in that part of it now known as Germany.[1][2][3] 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 was a religious man of God and found it his duty to help man discover God's creation through numbers and calculations. Kepler entered the Lutheran seminary at Adelberg in 1584,[2] and in 1589 he won a scholarship to study theology at the University of Tübingen.[3]

At this time, mathematics was often taught blindly and with little understanding of its concepts. Indeed, 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][2] While at Graz, Kepler wrote his famous Mysterium Cosmographicum, the first forthright and public defense of Copernican heliocentrism.[3]

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][2] There he became the assistant to Tycho Brahe, court mathematician to Holy Roman Emperor Rudolf II, who had taken no firm position on the Catholic-Lutheran conflict.[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,[3] the highest ranking in Europe at the time.[2] After reading and studying the data that Tycho had developed and researched, Kepler was able to resolve and calculate the orbit of Mars — as an ellipse, not a circle. Kepler recorded the order that he was able to come to this theory, which we commonly now call the Scientific Method.

Kepler remained as Imperial Mathematician until 1612, when Rudolf II was deposed.[2] 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.[2] He died in 1630, at Regensberg.[2][3]

Kepler's contributions to astronomy

From Tycho Brahe's records of observations, 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.

Very few of his fellow scientists appreciated this link. 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, observations he made once he acquired a suitable telescope.[2]

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 1 AD.[4] 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).[3] His last work was the Rudolphine Tables (named for Rudolf II), completing 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.[3]


Kepler was a man of many discoveries and contributions that we see around us every day. Because of him, we are able to appreciate the stars and planets without wondering how our earth, sun and moon rotates, the scientific method, the exact birth date of Jesus, explain how a telescope works, and understand and use logarithms.

Related References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Dao, Christine. "Man of Science, Man of God: Johann Kepler." Institute for Creation Research. Accessed March 2, 2008.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Van Helden, Al. "Johannes Kepler (1571-1630)." The Galileo Project, Rice University, 1995. Accessed March 2, 2008.
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 "Johannes Kepler: His Life, His Laws, and Times." NASA. Accessed March 2, 2008.
  4. James Ussher might have used those calculations in his Annals to fix the date of Christ's birth and the Crucifixion.