Jakob BARSCHIUS, German astronomer & Kepler

["Claudio Antonini" <claudio_antonini@xxxxxxxxxxx>]

Note below the mentions to Prague, Rudolph II, Kepler, Jakob Barscht (who 
become Kepler's son in law the same year that Kepler died), and other 
interesting events of the times. A few dates, the 1615-16 witch hunt and a 
work from Kepler concerning 'uterus' might also be of interest.

I don't remember where it comes from, but Barschius was alternatively 
spelled as Baresch, which is not far from 'Bartsch'.

The following is from 
http://es.rice.edu/ES/humsoc/Galileo/People/kepler.html, found using 
Altavista.

"Except for Mercury, Kepler's construction produced remarkably accurate 
results. Because of his talent as a mathematician, displayed in this volume, 
Kepler was invited by Tycho Brahe to Prague to become his assistant and 
calculate new orbits for the planets from Tycho's observations. Kepler moved 
to Prague in 1600.

Kepler served as Tycho Brahe's assistant until the latter's death in 1601 
and was then appointed Tycho's successor as Imperial Mathematician, the most 
prestigious appointment in mathematics in Europe. He occupied this post 
until, in 1612, Emperor Rudolph II was deposed. In Prague Kepler published a 
number of important books. In 1604 Astronomia pars Optica ("The Optical Part 
of Astronomy") appeared, in which he treated atmospheric refraction * but 
also treated lenses and gave the modern explanation of the workings of the 
eye; in 1606 he published De Stella Nova ("Concerning the New Star") on the 
new star that had appeared in 1604; and in 1609 his Astronomia Nova ("New 
Astronomy") appeared, which contained his first two laws (planets move in 
elliptical orbits with the sun as one of the foci, and a planet sweeps out 
equal areas in equal times). Whereas other astronomers still followed the 
ancient precept that the study of the planets is a problem only in 
kinematics, Kepler took an openly dynamic approach, introducing physics into 
the heavens.

In 1610 Kepler heard and read about Galileo's discoveries with the spyglass. 
He quickly composed a long letter of support which he published as 
Dissertatio cum Nuncio Sidereo ("Conversation with the Sidereal Messenger"), 
and when, later that year, he obtained the use of a suitable telescope, he 
published his observations of Jupiter's satellites under the title Narratio 
de Observatis Quatuor Jovis Satellitibus ("Narration about Four Satellites 
of Jupiter observed"). These tracts were an enormous support to Galileo, 
whose discoveries were doubted or denied by many. Both of Kepler's tracts 
were quickly reprinted in Florence. Kepler went on to provide the beginning 
of a theory of the telescope in his Dioptrice, published in 1611.

During this period the Keplers had three children (two had been born in Graz 
but died within months), Susanna (1602), who married Kepler's assistant 
Jakob Bartsch in 1630, Friedrich (1604-1611), and Ludwig (1607-1663). 
Kepler's wife, Barbara, died in 1612. In that year Kepler accepted the 
position of district mathematician in the city of Linz, a position he 
occupied until 1626. In Linz Kepler married Susanna Reuttinger. The couple 
had six children, of whom three died very early.

In Linz Kepler published first a work on chronology and the year of Jesus's 
birth, In German in 1613 and more amply in Latin in 1614: De Vero Anno quo 
Aeternus Dei Filius Humanam Naturam in Utero Benedictae Virginis Mariae 
Assumpsit (Concerning the True Year in which the Son of God assumed a Human 
Nature in the Uterus of the Blessed Virgin Mary"). In this work Kepler 
demonstrated that the Christian calendar was in error by five years, and 
that Jesus had been born in 4 BC, a conclusion that is now universally 
accepted. Between 1617 and 1621 Kepler published Epitome Astronomiae 
Copernicanae ("Epitome of Copernican Astronomy"), which became the most 
influential introduction to heliocentric astronomy; in 1619 he published 
Harmonice Mundi ("Harmony of the World"), in which he derived the 
heliocentric distances of the planets and their periods from considerations 
of musical harmony. In this work we find his third law, relating the periods 
of the planets to their mean orbital radii.

In 1615-16 there was a witch hunt in Kepler's native region, and his own 
mother was accused of being a witch. It was not until late in 1620 that the 
proceedings against her ended with her being set free. At her trial, her 
defense was conducted by her son Johannes.

1618 marked the beginning of the Thirty Years War, a war that devastated the 
German and Austrian region. Kepler's position in Linz now became 
progressively worse, as Counter Reformation * Counter Reformation measures 
put pressure on Protestants in the Upper Austria province of which Linz was 
the capital. Because he was a court official, Kepler was exempted from a 
decree that banished all Protestants from the province, but he nevertheless 
suffered persecution. During this time Kepler was having his Tabulae 
Rudolphinae ("Rudolphine Tables") printed, the new tables, based on Tycho 
Brahe's accurate observations, calculated according to Kepler's elliptical 
astronomy. When a peasant rebellion broke out and Linz was besieged, a fire 
destroyed the printer's house and shop, and with it much of the printed 
edition. Soldiers were garrisoned in Kepler's house. He and his family left 
Linz in 1626. The Tabulae Rudolphinae were published in Ulm in 1627.

Kepler now had no position and no salary. He tried to obtain appointments 
from various courts and returned to Prague in an effort to pry salary that 
was owed him from his years as Imperial Mathematician from the imperial 
treasury. He died in Regensburg in 1630. Besides the works mentioned here, 
Kepler published numerous smaller works on a variety of subjects."




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