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Johannes Kepler (December 27, 1571 – November 15, 1630), a key figure in the scientific revolution, was a German mathematician, astronomer, astrologer, and an early writer of science fiction stories. He is best known for his laws of planetary motion, based on his works Astronomia nova, Harmonice Mundi and the textbook Epitome of Copernican Astronomy. Through his career Kepler was a mathematics teacher at a Graz seminary school (later the University of Graz, Austria), an assistant to Tycho Brahe, court mathematician to Emperor Rudolf II, mathematics teacher in Linz, Austria, and court astrologer to General Wallenstein. He also did fundamental work in the field of optics and helped to legitimize the telescopic discoveries of his contemporary Galileo Galilei. He is sometimes referred to as "the first theoretical astrophysicist", although Carl Sagan also referred to him as the last scientific astrologer.
Childhood and education (1571&1594) Kepler was born at 2:30 PM on December 27 1571 at the Imperial Free City of Weil der Stadt (now part of the Stuttgart Region in the German state of Baden-Württemberg, 30 km west of Stuttgart's center). His grandfather had been Lord Mayor of that town, but by the time Johannes was born, the Kepler family fortunes were in decline. His father earned a precarious living as a mercenary, and he left the family when Johannes was five years old. He was believed to have died in the war in the Netherlands. His mother, an inn-keeper's daughter, was a healer and herbalist who was later tried for witchcraft. Whether Kepler was born prematurely is disputable. But it is indisputable that he was frequently ill. Despite his ill health, he was precociously brilliant. As a child, he often impressed travelers at his grandfather's inn with his phenomenal mathematical faculty. He was introduced to astronomy/astrology at an early age, and he developed a love for it that would span his entire life. At age five, he observed the Comet of 1577, writing that he "was taken by his mother to a high place to look at it." At age nine, he observed another astronomical event, the Lunar eclipse of 1580, recording that he remembered being "called outdoors" to see it and that the moon "appeared quite red". However, childhood smallpox left him with weak vision, limiting him to the mathematical rather than observational aspects of astronomy. In 1589, after moving through grammar school, Latin school, and after passing the "Landexamen" (state-wide examination), Kepler attended the lower and higher seminary in the scholarship-based education system of the Duchy of Württemberg. Kepler immatriculated in the University of Tübingen as a theology student, where he proved himself to be a superb mathematician and earned a reputation as a skillful astrologer. Under the instruction of Michael Maestlin, he learned both the Ptolemaic system and the Copernican system; he became a Copernican at that time, defending heliocentrism from both a theoretical and theological perspective in student debates. Despite his desire to become a minister, near the end of his studies, Kepler was recommended for a position as teacher of mathematics and astronomy at the Protestant school in Graz, Austria. He accepted the position in April 1594, at the age of 23. Early career (1594&1601) In Graz, Kepler began developing an original theory of cosmology based on the Copernican system, which was published in 1596 as Mysterium Cosmographicum—The Sacred Mystery of the Cosmos. In April 1597, Kepler married Barbara Müller. She died in 1611 and was outlived by two of Johannes's children and one by an earlier marriage. In December 1599, Tycho Brahe wrote to Kepler, inviting Kepler to assist him at Benátky nad Jizerou outside Prague. Pressured to leave Graz by increasingly strict Counter-Reformation policies restricting the religious practices and political rights of Protestants, Kepler joined Tycho in 1600. After Tycho's death in 1601, Kepler was appointed Imperial Mathematician in his place, a post he would retain through the reigns of three Habsburg Emperors (from November 1601 to 1630). Imperial Mathematician in Prague (1601&1612) As Imperial Mathematician, Kepler inherited Tycho's responsibility for the Emperor's horoscopes as well as the commission to produce the Rudolphine Tables. Working with Tycho's extensive collection of highly accurate observational data, Kepler also set out to refine his earlier theories but was forced to abandon them. Instead, he began developing the first astronomical system to use non-circular orbits; it was completed in 1606 and published in 1609 as Astronomia Nova—New Astronomy. Astronomia Nova contained what would become the first and second laws of planetary motion. In October 1604, Kepler observed the supernova which was subsequently named Kepler's Star (a term which may also refer to the stellated octahedron). In 1611, Kepler published (as a letter to a friend) a monograph on the origins of snowflakes, the first known work on the subject. He correctly theorized that their hexagonal nature was due to cold, but did not ascertain a physical cause for this. In January 1612, the Emperor died. To escape the growing religious tension in Prague, Kepler took the post of Provincial Mathematician in Linz. Teaching in Linz and final years (1612&1630) In 1615, Kepler married Susanna Ruettinger, with whom he would have several children. In 1617, Kepler's mother Katharina was accused of being a witch in Leonberg. Beginning in August 1620 she was imprisoned for fourteen months. Thanks in part to the extensive legal defense drawn up by Kepler, she was released in October 1621 after failed attempts to convict her. However, she was subjected to territio verbalis, a graphic description of the torture awaiting her as a witch, in a final attempt to make her confess. Throughout the trial, Kepler postponed his other work (on the Rudolphine Tables and a multi-volume astronomy textbook) to focus on his "harmonic theory". The result, published in 1619 as Harmonices Mundi ("Harmony of the Worlds") contained the third law of planetary motion. Kepler completed the last of seven volumes of his textbook Epitome of Copernican Astronomy in 1621, which brought together and extended his previous work and would become very influential in the acceptance of the Copernican system over the next century. In 1627 he completed the Rudolphine Tables, which provided accurately calculated future positions of the planets and allowed the prediction of rare astronomical events. On November 15, 1630 Kepler died of a fever in Regensburg. In 1632, only two years after his death, his grave was demolished by the Swedish army in the Thirty Years' War. Kepler had incidentally composed the epitaph for his own tombstone, which read: I measured the skies, now the shadows I measure, Work Kepler lived in an era when there was no clear distinction between astronomy and astrology, while there was a strong division between astronomy/astrology (a branch of mathematics within the liberal arts) and physics (a branch of the more prestigious discipline of philosophy). He also incorporated religious arguments and reasoning into his work, such that the basis for many of his most important contributions was essentially theological (Barker & Goldstein, 2001). Kepler was a Pythagorean mystic. He considered mathematical relationships to be at the base of all nature, and all creation to be an integrated whole. This was in contrast to the Platonic and Aristotelian notion that the Earth was fundamentally different from the rest of the universe, being composed of different substances and with different natural laws applying. In his attempt to discover universal laws, Kepler applied terrestrial physics to celestial bodies; famously, his effort produced the three Laws of Planetary Motion. Kepler was also convinced that celestial bodies influence terrestrial events. One result of this belief was his correct assessment of the moon's role in generating the tides, years before Galileo's incorrect formulation. Another was his belief that someday it would be possible to develop a "scientific astrology", despite his general disdain for most of the astrology of his time. Keplers laws
Supernova 1604 On October 17, 1604, Kepler observed that an exceptionally bright star had suddenly appeared in the constellation Ophiuchus. (It was first observed by several others on October 9.) The appearance of the star, which Kepler described in his book De Stella nova in pede Serpentarii ("On the New Star in Ophiuchus's Foot"), provided further evidence that the cosmos were not changeless; this was to influence Galileo Galilei in his argument. It has since been determined that the star was a supernova, the second in a generation, later called Kepler's Star or Supernova 1604. No further supernovae have been observed in the Milky Way, though others outside our galaxy have been seen. Other scientific and mathematical work Kepler also made fundamental investigations into combinatorics, geometrical optimization, and natural phenomena such as snowflakes, always with an emphasis on form and design. He was also one of the founders of modern optics, defining for example antiprisms and the Kepler telescope (see Kepler's books Astronomiae Pars Optica—i.a. theoretical explanation of the camera obscura—and Dioptrice). In addition, since he was the first to recognize the non-convex regular solids (such as the stellated dodecahedra), they are named Kepler solids in his honor. Kepler also was in contact with Wilhelm Schickard, inventor of the first automatic calculator, whose letters to Kepler show how to use the machine for calculating astronomical tables. Mysticism
Astrology Kepler disdained astrologers who pandered to the tastes of the common man without knowledge of the abstract and general rules, but he saw compiling prognostications as a justified means of supplementing his meager income. Yet, it would be a mistake to take Kepler's astrological interests as merely pecuniary. As one historian, John North, put it, "had he not been an astrologer he would very probably have failed to produce his planetary astronomy in the form we have it." However, Kepler's views on astrology were quite unconventional for his time; he argued for a system of astrology based largely on harmonics, a type of 'planetary harmonics' based almost entirely upon the astrological aspects and what has been traditionally been termed "the music of the spheres." Information relating to his theories can be found in his book Harmonice Mundi. Kepler believed in astrology in the sense that he was convinced that astrological aspects physically and really affected humans as well as the weather on Earth. He strove to unravel how and why that was the case and tried to put astrology on a surer footing, which resulted in the On the More Certain Fundamentals of Astrology (1601), in which, among other technical innovations, he was the first to propose a number of new aspects such as 18°, 24°, 30° (semi-sextile), 36°, 45° (semi-square), 72° (quintile), 108°, 135° (sesquiquadrate), 144° (bi-quintile), and 150° (quincunx). In The Intervening Third Man, or a warning to theologians, physicians and philosophers (1610), posing as a third man between the two extreme positions for and against astrology, Kepler advocated that a definite relationship between heavenly phenomena and earthly events could be established. At least 800 horoscopes and natal charts drawn up by Kepler are still extant, several of himself and his family, accompanied by some unflattering remarks. As part of his duties as district mathematician to Graz, Kepler issued a prognostication for 1595 in which he forecast a peasant uprising, Turkish invasion and bitter cold, all of which happened and brought him renown. Kepler is known to have compiled prognostications for 1595 to 1606, and from 1617 to 1624. As court mathematician, Kepler explained to Rudolf II the horoscopes of the Emperor Augustus and the Prophet Muhammad, and Kepler gave astrological prognosis for the outcome of a war between the Republic of Venice and Paul V. In the On the new star (1606) Kepler explicated the meaning of the new star of 1604 as the conversion of America, downfall of Islam and return of Christ. The De cometis libelli tres (1619) is also replete with astrological predictions. Writings by Kepler
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