**Johannes Kepler (1571-1630)**

Johannes Kepler invented log books that he used as a tool for calculating planetary positions, eyeglasses for near and far sighted persons, the convex eyepiece, and the quintile and biquintile (astronomy) aspects. Aside from his inventions, Johannes Kepler also contributed discoveries and theories to several sciences including astronomy and optics.

**Biography**

Johannes Kepler was born at 2:30
PM on December 27, 1571, in Weil der Stadt, Württemburg, in the Holy
Roman Empire. He was a sickly child and his parents were poor. But his
evident intelligence earned him a scholarship to the University of Tübingen
to study for the Lutheran ministry. There he was introduced to and delighted
in the ideas of Copernicus. In 1596, while a mathematics teacher in Graz,
he wrote the first outspoken defense of the Copernican system, the "Mysterium
Cosmographicum".

Johannes Kepler's family was Lutheran
and he adhered to the* "*Augsburg Confession" a defining document
for Lutheranism. However, he did not adhere to the Lutheran position on
the real presence and refused to sign the "Formula of Concord". Because
of his refusal he was excluded from the sacrament in the Lutheran church.
This and his refusal to convert to Catholicism left him alienated by both
the Lutherans and the Catholics. Thus he had no refuge during the Thirty-Years
War.

Johannes Kepler was forced to leave his teaching post at Graz due to the counter Reformation because he was Lutheran and moved to Prague to work with the renowned Danish astronomer, Tycho Brahe. He inherited Tycho's post as Imperial Mathematician when Tycho died in 1601. Using the precise data that Tycho had collected, Kepler discovered that the orbit of Mars was an ellipse. In 1609 he published "Astronomia Nova", delineating his discoveries, which are now called Kepler's first two laws of planetary motion. And what is just as important about this work, "it is the first published account wherein a scientist documents how he has coped with the multitude of imperfect data to forge a theory of surpassing accuracy" (O. Gingerich in forward to Johannes Kepler New Astronomy translated by W. Donahue, Cambridge Univ Press, 1992), a fundamental law of nature. Today we call this the scientific method.

In 1612 Lutherans were forced out of Prague, so Kepler moved on to Linz. His wife and two sons had recently died. He remarried happily, but had many personal and financial troubles. Two infant daughters died and Kepler had to return to Württemburg where he successfully defended his mother against charges of witchcraft. In 1619, he published "Harmonices Mundi", in which he describes his "third law."

In spite of more forced relocations, Kepler published the seven-volume "Epitome Astronomiae" in 1621. This was his most influential work and discussed all of heliocentric astronomy in a systematic way. He then went on to complete the Rudolphine Tables that Tycho had started long ago. These included calculations using logarithms, which he developed, and provided perpetual tables for calculating planetary positions for any past or future date. Kepler used the tables to predict a pair of transits by Mercury and Venus of the Sun, although he did not live to witness the events.

Johannes Kepler died in Regensburg in 1630, while on a journey from his home in Sagan to collect a debt. His grave was demolished within two years because of the Thirty Years War. Frail of body, but robust in mind and spirit, Kepler was scrupulously honest to the data.

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**A List of Johannes
Kepler's Firsts**

In Johannes Kepler's book "Astronomia Pars Optica", for which he earned the title of founder of modern optics he was the:First to correctly explain planetary motion, thereby, becoming founder of celestial mechanics and the first "natural laws" in the modern sense; being universal, verifiable, precise.

In Johannes Kepler's book "Dioptrice" (a term coined by Kepler and still used today) he was the:First to investigate the formation of pictures with a pin hole camera; First to explain the process of vision by refraction within the eye; First to formulate eyeglass designing for nearsightedness and farsightedness; First to explain the use of both eyes for depth perception.

In addition:First to describe: real, virtual, upright and inverted images and magnification; First to explain the principles of howa telescope works;First to discover and describe the properties of total internal reflection.

His book "Stereometrica Doliorum" formed the basis of integral calculus. First to explain that the tides are caused by the Moon (Galileo reproved him for this). Tried to use stellar parallax caused by the Earth's orbit to measure the distance to the stars; the same principle as depth perception. Today this branch of research is called astrometry. First to suggest that the Sun rotates about its axis in "Astronomia Nova" First to derive the birth year of Christ, that is now universally accepted. First to derive logarithms purely based on mathematics, independent of Napier's tables published in 1614.

He coined the word "satellite" in his pamphlet "Narratio de Observatis a se quatuor Iovis sattelitibus erronibus"

**Related Information**

**Johannes Kepler - biography**

Information courtesy of Kepler Mission, NASA