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nHendidn’t get the credit, but he did get to name stuff…
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nSimonnMarius was a German astronomer and one of the earliest users ofntelescopes. He discovered and named the four largest moons ofnJupiter—
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nWaitna minute! If you know your astronomical history, you know that it wasnGalileo Galilei who discovered the four largest moons of Jupiter! That’s why they’re called the Galilean moons!
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n However…
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Therenis this thing called “priority” in scientific discoveries. SimonnMarius claimed to have seen (in other words, discovered) the Joviannmoons before Galileo did, and he published his claim and observationsnin 1614. However, Galileo had published his diagrams of the Joviannmoons four years before Marius, in 1610; Galileo pointed out thatnMarius’s diagram matched his earlier-published diagram. It isnpossible that the two astronomers first spotted the moons on the verynsame day, or that Marius copied Galileo’s diagram, but most peoplenthink that Marius discovered the moons independently but a bit laternthan Galileo.
Therenis this thing called “priority” in scientific discoveries. SimonnMarius claimed to have seen (in other words, discovered) the Joviannmoons before Galileo did, and he published his claim and observationsnin 1614. However, Galileo had published his diagrams of the Joviannmoons four years before Marius, in 1610; Galileo pointed out thatnMarius’s diagram matched his earlier-published diagram. It isnpossible that the two astronomers first spotted the moons on the verynsame day, or that Marius copied Galileo’s diagram, but most peoplenthink that Marius discovered the moons independently but a bit laternthan Galileo.n
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nItndidn’t help, when trying to figure out priority, that the two mennused different calendars. According to his notes, Simon Mariusndiscovered the moons on December 29, 1609; according to Galileo’snrecord, he discovered the moons on January 7, 1610. So Marius wasnfirst, right?
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nWell,nGalileo used the Gregorian calendar, whereas Marius used the Julianncalendar. Translating Marius’s date to the Gregorian calendar (whichnwe use today), Marius made his discovery on January 8, 1610.
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nOoo,nso close!
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nMariusnpointed out that he looked at Jupiter a month or two before and hadnseen the moons then—but he didn’t write or draw anything. This isnwhat is known as an unrecorded observation; it doesn’t count.
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| Callisto |
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| Ganymede |
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nSonGalileo gets the credit for the discovery. Interestingly enough,nhowever, we use the names that Marius gave the moons: Io, Callisto,nGanymede, and Europa. Perhaps that’s because Galileo just named thenmoons I, II, III, and IV!
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| Europa |
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| Io |
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nFindnout more about Simon Marius innthis earlier post.
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nAlsonon this date:
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nAstronomer Robert Woodrow Wilson’s birthday
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nAnniversary of first subway
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nAnniversary of first aerial photo in U.S.
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nAnniversary of a successful Amelia Earhart flight
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