Simon Marius

Simon Marius (latinized form of Simon Mayr; 10 January 1573 – 5 January 1625) was a German astronomer. He was born in Gunzenhausen, near Nuremberg, but spent most of his life in the city of Ansbach. He is most known for being among the first observers of the four largest moons of Jupiter, and his publication of his discovery led to charges of plagiarism.

Early life

Marius was the son of Reichart Mayr, a mayor of Gunzenhausen. On the recommendation of George Frederick, Margrave of Brandenburg-Ansbach, he was admitted to the Margrave's Academy in Heilsbronn in 1586, where he studied until 1601. During this time, he published observations about a comet as well as astronomical tables, which gave him a reputation as a good astronomer and mathematician, and the Margrave appointed him as his official mathematician. Marius wanted to attend the University of Königsberg, but was unable to get a scholarship. However, the Margrave wrote a letter of recommendation on 22 May 1601, so that Marius could study in Prague under Tycho Brahe, which he did for several months, although he may actually have worked directly with David Fabricius instead of Brahe himself.

By September 1601, Marius had already left Prague and he arrived in Padua in December 1601 to study medicine at the University of Padua. During this time, he tutored other students in astronomy, including one Baldassarre Capra, with whom he wrote a book on a new star (actually Kepler's Supernova) they observed in 1604. Capra had a dispute with Galileo Galilei (both of them learned fencing from Capra's father) on the invention of the proportional compass and Marius took his student's side in the argument. Marius left the school in July 1605, returning to Ansbach to become the mathematician and physician to the new Margraves, Christian and Joachim Ernst.

In 1606, Marius married Felicitas Lauer (born 1590), the daughter of his publisher, in Ansbach, and in 1609 he published the first German translations of Euclid's Elements. That year, he also built his own telescope and in November made observations of the Galilean moons, slightly before Galileo did himself, which became the source of a major dispute between the two.