|Died||January 5, 1625 (aged 51)|
Ansbach, Principality of Ansbach
|Known for||Jupiter, Andromeda Galaxy|
Simon Marius (Latinized from German Simon Mayr; January 20, 1573 - January 5, 1625) was a German astronomer. He was born in Gunzenhausen, near Nuremberg, but he spent most of his life in the city of Ansbach. He is most noted for making the first observations of the four largest moons of Jupiter, before Galileo himself, and his publication of his discovery led to charges of plagiarism.
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 May 22, 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, the daughter of his publisher, in Nuremberg, 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.
Capra published another book in 1607 which he actually plagiarised from Galileo, and Marius was implicated in the act due to his prior association with Capra, even though this was after Marius had left Padua. Galileo certainly was under that impression, as he referred to his "old adversary" (without explicitly naming Marius) as a "poisonous reptile", and an "enemy of all mankind".
In 1614, Marius published his work Mundus Iovialis describing the planet Jupiter and its moons (he previously had published the discovery in 1611 in a local almanac). Here he claimed to have discovered the planet's four major moons about a month before Galileo, who was naturally incensed. In The Assayer in 1623, he accused Marius of plagiarism.
Because of Galileo's stature in the scientific community, for nearly 300 years, Marius's reputation was tainted by Galileo's accusations. However, a jury in the Netherlands in 1903 examined the evidence extensively and ruled in favor of Marius's independent discoveries, with results published by Bosscha in 1907. Apparently Marius discovered the moons independently, but did not start keeping notes until December 29, 1609. Marius used the Julian calendar, and that date is equivalent to January 8, 1610, in the Gregorian one used by Galileo, one day after Galileo's letter in which he first described the moons.
Io, Europa, Ganimedes puer, atque Calisto
Discussion of Marius' work is scarce, but what exists tends to note his skill as an observer, including:
Marius drew conclusions about the structure of the universe from his observations of the Jovian moons and the stellar disks. The stellar disks he observed were spurious (likely the Airy disk caused by diffraction, as stars are too distant for their physical disks to be detected telescopically), but Marius interpreted them to be physical disks, like the planetary disks visible through a telescope. He concluded that since he could see stellar disks, the stars could not be as distant as was required in the Copernican world system, and he said that the appearance of the stars as seen through a telescope actually argued against Copernicus. He also concluded from his observations of the Galilean moons that they must orbit Jupiter while Jupiter orbits the Sun. Therefore, Marius concluded that the geocentric Tychonic system, in which the planets circle the Sun while the Sun circles the Earth, must be the correct world system, or model of the universe.