Simon Marius facts for kids

Quick facts for kids Simon Marius
Engraving of Marius in his book Mundus Iovialis (World of Jupiter), 1614
Born	Simon Mayr (1573-01-10)10 January 1573 Gunzenhausen, Principality of Ansbach
Died	5 January 1625(1625-01-05) (aged 51) Ansbach, Principality of Ansbach
Nationality	German
Known for	Naming the four largest moons of Jupiter, studying Andromeda Galaxy, Jupiter
Scientific career
Fields	Astronomy

Simon Marius (whose name was changed to a more Latin form, Simon Mayr; born January 10, 1573 – died January 5, 1625) was a German astronomer. He was born in Gunzenhausen, a town near Nuremberg. He spent most of his life in the city of Ansbach. He is best known for being one of the first people to see the four biggest moons of Jupiter. His book about this discovery led to a big argument about who saw them first.

Early Life and Studies

Simon Marius was the son of Reichart Mayr, who was the mayor of Gunzenhausen. In 1586, he started studying at the Margrave's Academy in Heilsbronn. He stayed there until 1601. During this time, he wrote about a comet he saw. He also made special charts for stars. This made him known as a good astronomer and mathematician. The Margrave then made him his official mathematician.

Marius wanted to go to the University of Königsberg, but he could not get a scholarship. However, the Margrave wrote a letter for him in 1601. This letter helped Marius study in Prague with Tycho Brahe for a few months. He might have worked more closely with David Fabricius.

By December 1601, Marius was in Padua to study medicine at the University of Padua. While there, he taught other students about astronomy. One of his students was Baldassarre Capra. They wrote a book together about a new star they saw in 1604. This star was actually Kepler's Supernova. Capra had a disagreement with Galileo Galilei about who invented the proportional compass. Marius supported his student in this argument. Marius left the school in 1605. He went back to Ansbach to work as a mathematician and doctor for the new Margraves, Christian and Joachim Ernst.

In 1606, Marius married Felicitas Lauer in Ansbach. She was born in 1590 and was the daughter of his publisher. In 1609, he published the first German translations of Euclid's Elements. That same year, he built his own telescope. In November, he saw the Galilean moons. He saw them a little before Galileo did. This became the start of a major disagreement between the two scientists.

Disagreement with Galileo

In 1607, Capra published another book. It turned out he had copied parts of it from Galileo. Marius was linked to this because he had worked with Capra before. Even though Marius had already left Padua, Galileo thought Marius was involved. Galileo called his "old enemy" (without saying Marius's name) a "poisonous reptile" and an "enemy of all mankind."

In 1614, Marius published his book Mundus Iovialis. This means World of Jupiter in English. In it, he wrote about the planet Jupiter and its moons. He had already shared his discovery in a local newspaper in 1611. In his book, he said he found Jupiter's four main moons about a month before Galileo. Galileo was very angry about this. In his book The Assayer in 1623, Galileo said Marius had copied his work.

Because Galileo was so famous, Marius's good name was damaged for almost 300 years. People believed Galileo's claims. However, in 1903, a group of experts in the Netherlands looked at all the facts. They decided that Marius had found the moons on his own. Their findings were published in 1907. It seems Marius did discover the moons independently. But he only started writing down his observations on December 29, 1609. Marius used the Julian calendar. This date is the same as January 8, 1610, on the Gregorian calendar. This was one day after Galileo first wrote about the moons.

No matter who saw them first, the names we use for these moons today come from Marius. He named them Io, Europa, Ganymede, and Callisto. These names come from old myths:

Key Discoveries

Simon Marius also observed the Andromeda "nebula". This fuzzy patch of light in the sky was also known to Persian astronomers long ago.

Not much is written about Marius's work. But what we know shows he was a very skilled observer. Here are some of his observations:

• In 1612, he measured the size of the Andromeda nebula. He saw it had a faint, pale light that got brighter in the middle. He said it looked like "a candle shining through horn."
• He noticed fake circles around stars when looking through his telescope. These were caused by the telescope itself.
• From watching Jupiter's moons, he figured out their orbits better than Galileo did.
• He found the spot where Tycho Brahe's supernova of 1572 had been. He saw a star there that he thought was "a bit dimmer than Jupiter's third moon."

Marius used his observations of Jupiter's moons and the star circles to understand the universe better. The circles he saw around stars were not real. They were caused by light bending (called diffraction). Stars are too far away to see their actual sizes through a telescope. But Marius thought these circles were real, like the planets he could see. He believed that if he could see star circles, then stars could not be as far away as the Copernican system said. The Copernican system said the Earth and planets orbit the Sun. Marius thought what he saw through his telescope went against Copernicus's idea.

Galileo, however, used similar telescope data to support the Copernican system. Galileo believed in the Copernican idea because it seemed mathematically grand. Marius, though, did not seem to favor any one theory. He made his guesses based only on what he saw through his telescope. He also concluded that Jupiter's moons must orbit Jupiter while Jupiter orbits the Sun. Because of this, Marius thought the Tychonic system was the correct model of the universe. In the Tychonic system, the planets orbit the Sun, but the Sun still orbits the Earth.

Works by Simon Marius

• Mundus Iovialis anno MDCIX Detectus Ope Perspicilli Belgici (The World of Jupiter, Discovered in 1609 with the Belgian Telescope), 1614. This book is available in Latin and with a German translation.
• Zinner, E., "Zur Ehrenrettung des Simon Marius" (To Restore Simon Marius's Honor), in: Vierteljahresschrift der Astronomischen Gesellschaft, 77. Jahrgang, 1. Heft, Leipzig 1942.
• Bosscha, J., "Simon Marius. Réhabilitation d´un astronome calomnié" (Simon Marius. Rehabilitation of a Slandered Astronomer), in: Archives Nederlandaises des Sciences Exactes et Naturelles, Ser. II, T. XII, pp. 258–307, 490–528, La Haye, 1907.

See also

In Spanish: Simon Marius para niños