Erhard Weigel

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**Erhard Weigel**
Erhard Weigel
Born	16 December 1625 Weiden in der Oberpfalz
Died	20 March 1699 Jena, Germany
Residence	Germany
Nationality	German
Field	Mathematician, astronomer and philosopher
Institution	University of Jena
Alma mater	University of Leipzig
Notable students	Gottfried Wilhelm von Leibniz
Known for	Introduction of Gregorian calendar

Erhard Weigel (1625–1699) was a German mathematician, astronomer and philosopher.

He earned his Ph.D. from the University of Leipzig. From 1653 until his death in 1699, he was professor of mathematics at the Jena University. He is noted as the teacher of Leibniz in 1663, and other notable students. He also worked to make science more widely accessible to the public, or, what could be considered today a popularizer of science.

Based on his recommendation and the advocacy of Leibniz and others, the date of Easter became based on the astronomical measurement of the spring equinox and the next full Moon. He also approached the Protestant princes of the period to advocate the use of the Gregorian calendar.

Weigel crater on the Moon is named after him. In 1999 a colloquim was held in Jena on the 300th anniversary of his death.

1625, 16 December in Weiden in der Oberpfalz, as son of the clothier Michael Weigel and Anna Weigel.
1627-28 seizures of the head palatinate through imperial troops starting with Rekatholisierung; Escape of the Weigel family from Wunsiedel to Markgrafschaft Ansbach-Bayreuth
1628-44 teens year at the grammar school in Wunsiedel
1644-46 Lutheran high school in Halle (Saale) and simultaneous activity with the astronomer Bartholomäus Schimpfer, who teaches him mathematics.
1646 temporary return to Wunsiedel; Mathematics and astronomy instruction with archdeacon Jakob Ellrod
1647-50 studies at the University of Leipzig
1650 doctorate in philosophy
1652 habilitations in Leipzig with Dissertatio Metaphysica Prior (De Existentia) und Posterior (De Modo Existentiae, qui dicitur Duratio)
1653 post as mathematics professor in Jena
1653, 16 July, commencement of lectures De Cometa Novo (regarding the comet of December 1652)
1653 married Elisabeth Hartmann (a widow) on September 12
1654 appointment as Stipendiarorum et Alumnorum Inspector (supervision over the Collegium Jenense)
1658 publishes the analysis Aristotelica ex Euclide restituta, genuinum sciendi modum, & nativam restauratae Philosophiae faciem per omnes disciplinas & facultates ichnographicè depingens. The work brings him in conflict with the philosophical faculty.
1661 publishes Himmelsspiegels (Speculum Uranicum / Aquilae Romanae Sacrum...).
1663 Gottfried Wilhelm Leibniz, studies one semester in Jena, among others under Erhard Weigel.
1664 publishes of the Speculum Temporis Civilis; contains explanation of the calendar
1665 publishes Speculum Terrae
1667-70 Weigel's house, in Jena, for its time has remarkable technical interior facilities - among others an elevator and a water pipe
1669 publishes Idea Matheseos Universae cum Speciminibus Inventionum Mathematicarum
1673 publications the Universi Corporis Pansophici Caput Summum.
1674 publishes an arithmetic description of morals
1679 Weigel's work on, "the mystery of Holy Trinity demonstrated from the principle of geometry", brings him in conflict with the theological faculty; he is forced to retract his work.
1683 wife Elisabeth dies
1688 appointed imperial advisor
1691 trip to England, to describe research results to the Royal Society; but he only comes as far as the coast where the weather prevents crossing the British Channel
1691 calls on the Dutch naturalist Christian Huygens to his estate
1693 publishes Philosophia Mathematica, Theologia Naturalis Solida
1695 becomes chancelor of the University of Jena
1699 Dies in Jena March 21st.