Johannes Kepler was born on December 27, 1571 in Weil der Stadt, Germany. Kepler’s grandfather was supposedly from a noble background, and once Mayor of Weil. However, Kepler’s father became a mercenary who narrowly avoided the gallows. Kepler’s mother, Katherine, was raised by an aunt who was eventually burned as a witch. In later years, Katherine herself was accused of Devil worship, and barely escaped from being burned at the stake. Kepler had six brothers and sisters, three of which, died in infancy. In his youth, Johannes was described as: “… ckly child, with thin limbs and a large, pasty face surrounded by dark curly hair. He was born with defective eyesight-myopia plus anocular polyopy (multiple vision).
His stomach and gall bladder gave constant trouble; he suffered from boils, rashes, and possibly from piles, for he tells us that he could never sit still for any length of time… ” (Koestler, p 24)From this inauspicious start, Johannes Kepler began his fascinating journey as a pioneer in astronomy. Johannes Kepler graduated from the Faculty of Arts at the University of Tuebingen at the age of twenty, intending to matriculate into the Theological Faculty.
It was here that Kepler learned and became an adherent of the heliocentric theory of planetary motion, first developed by the Dutch astronomer Nicolaus Copernicus. In 1594, Kepler left Tuebingen for the University of Graz to become a professor of astronomy. It was here that Kepler realized that figures of the type shown here determine a definite fixed ratio between the sizes of the two circles, provided the triangle has all sides equal, and a different ratio of sizes will occur for a square between the two circles, another for a regular pentagon, and so on.
Kepler believed that this could be used to determine the orbits of planets in the solar system. Unfortunately, Kepler proceeded from a false assumption: namely, that the orbits of the planet were circular. Despite the fact that his calculations did not match known planetary data, Kepler presumed that Copernicus’s data was in error, and produced this diagram of orbits, where the outer ring represents the orbit of Saturn. Kepler stayed at the University of Graz until 1600, when he was pressured to leave due to his Lutheran faith.
Kepler traveled to the observatory of the famed Danish Astronomer and Imperial Mathematician Tycho Brahe, where he became Brahe’s assistant. By all accounts, the relationship between the two was strained. We have previously discussed Kepler’s upbringing. In contrast, Brahe was from an aristocratic background who shared Kepler’s less than scintillating personality. As a result, the two continuously quarreled, and usually failed to resolve their academic and personal differences. However, the two realized that they needed each other.
As a result, both learned from each other’s writings. Brahe died in 1601, and Kepler assumed his post as imperial mathematicus. In addition, Rudolph II requested his service as court astronomer, which Kepler preformed until Rudolph’s death in 1612, During his tenure as court astronomer, Johannes Kepler labored over one of his most impressive works: Astronomia Nova. His primary motivation was to attempt to calculate the orbit of Mars. One offshot of this work was the formulation of the concepts that were eventually known as the first two of Kepler’s Laws.
In 1612, Kepler became provincial mathematician to Linz, in upper Austria. Over the next fourteen years, Kepler published Harmonice Mundi, in which Kepler outlined his third law. Furthermore, he published the Epitome Astronomiae Copernicanae, which combined all of his discoveries together. However, Kepler’s personal life was far less successful. His first wife, Barbara, and their two sons died from the fever and small pox in 1612. In 1615, Kepler was excommunicated from the church, and his mother was placed on trial for being a witch..
Despite these tribulations, Kepler completed the Tabulae Rudolfinae in 1625. These tables reduced the mean errors in tables of planetary motion significantly. However, political unrest led in the destruction of his home during a peasant revolt, leaving Kepler without a permanent residence. Johannes Kepler was named the private mathematicus in the newly acquired Duchy of Sagan in 1628. Unfortunately, neither this position nor his previous one was a lucrative profession due to the Thirty Years War.
As such, Kepler was left having to borrow money to travel to collect an old debt leaving his second wife and children behind, penniless. Sadly, he died en route on November 15, 1630 in the village of Ratisbon. Kepler, to this day, remains one of the greatest figures in astronomy. However, his endeavors were not just limited to this field. He is often called the founder of modern optics for his first use of eyeglasses designed for nearsightedness and farsightedness, his explanations of vision by refraction within the eyes, and his explanation of the use of both eyes for depth perception.
Furthermore, he explained the principles of the telescope. His book Stereometrica Doliorum formed the basis of integral calculus. First to explain that the tides are caused by the Moon (Galileo rebuked him for this). First to use stellar parallax caused by the Earth’s orbit to try to measure the distance to the stars; the same principle as depth perception. 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.
