Background
Christmann was born in November, 1554, in Johannisberg, Germany.
Grabengasse 1, 69117 Heidelberg, Germany
Christmann studied oriental subjects at Heidelberg University.
Christmann was born in November, 1554, in Johannisberg, Germany.
Christmann studied oriental subjects at Heidelberg and became a teacher there in 1580.
Christmann became a teacher at Heidelberg University in 1580. Shortly thereafter, however, he had to leave that university because he, as a Calvinist, could not subscribe to the concordat-formulary set down by the Lutheran Elector Ludwig VI. Christmann traveled for some time, then settled down to teach in a Reformed school in Neustadt. He was a teacher there in 1582. The death of Ludwig (12 October 1583) enabled him to return to Heidelberg, where he was appointed professor of Hebrew on 18 June 1584. From 1591 on he taught Aristotelian logic. He was made rector of the university in 1602.
In 1608 Frederick IV appointed Christmann professor of Arabic. Christmann thus became the second teacher of that subject in Europe, the first having been Guillaume Postel at Paris in 1538. This appointment must have given great satisfaction to its recipient, since in 1590, in the preface of his Alfragani chronologica et astronómica elementa, Christmann had advocated the establishment of a chair of Arabic. Indeed, Christmann had demonstrated his scholarly interest in the Arabic language as early as 1582, with the publication of his Alphabeticum Arabicum, a small book of rules for reading and writing Arabic. Besides Arabic, he is said to have known Syrian, Chaldaic, Greek, Latin, French, Italian, and Spanish.
On the death of Valentine Otho, Christmann inherited the entire library of G. J. Rhaticus, which had been in Otho’s keeping. This collection contained trigonometric tables more extensive than those that Rhaticus had published in the Opus Palatinum of 1596 as well as the original manuscript of Copernicus’ De revolutionibus orbium coelestium. The inclusion of instruments in the bequest stimulated Christmann to begin making astronomical observations.
In 1604 he proposed to Kepler that they should exchange the results of their researches. Christmann was the first to use the telescope in conjunction with such instruments as the sextant or Jacob’s staff (1611), with the results reported in his Theoria lunae and Nodus gordius. These last works also show him to be a competent astronomical theorist. He gave a good treatment of prosthaphaeresis, the best method of calculating trigonometric tables to be developed before the invention of logarithms; he then went on to prove that this method had been devised by Johann Werner. In his Tractatio geométrica de quadratura circuli, Christmann defended against J. J. Scaliger the thesis that the quadrature of the circle could be solved only approximately. In his books on chronology - a topic of great concern at a time of radical calendar reform - he disputed the work of not only Scaliger but also J. J. Lipsius. He further criticized Copernicus, Tycho Brahe, and Clavius - some such criticisms may be found in some detail in manuscript annotations of his own copy of Alfragani chronologica et astronómica elementa, which is now in the library of the University of Utrecht.
Christmann was an extremely modest man despite his learning, with a passion for work that may well have hastened his death of jaundice.