Slashdot Mirror
400 Years Ago, Galileo Discovered Four Jovian Moons
krswan writes "OK, the moons themselves are much older, but on January 7, 1610 Galileo first observed '4 fixed stars' surrounding Jupiter. Observations of their changing positions led Galileo to postulate they were really moons orbiting Jupiter, which became further evidence against Aristotelian Cosmology, which led to problems with the Roman Catholic Church, etc... Jupiter will be low in the southwest (in the Northern Hemisphere) after sunset this evening — nothing else around it is as bright, so you can't miss it. Celebrate by pointing binoculars or a telescope at Jupiter and checking out the moons for yourself."
To be fair, he also came up with this crazy-wrong idea about how the earth's motion was responsible for the tides.
To be fair, that's not entirely wrong. If the Earth rotated at different speeds the tides would be observably different.
Didn't they use a different calendar 400 years ago?
They did indeed use a different calendar 400 years ago in some countries, but the Italian states (where Galileo did his observations) had already adopted the Gregorian calendar by then.
"Little does he know, but there is no 'I' in 'Idiot'!"
A minor quibble with the summary above. On January 7, 1610, Galileo only recorded 3 "fixed stars" next to Jupiter. Two of the Galilean moons, Io and Europa, were too close together for Galileo to separate with his 20x power telescope. He continued to observe three moons at most, either because one or more moons were too close to Jupiter and were lost in the glare of the planet, Callisto was too far from Jupiter and was thus out of his telescope's field-of-view, or two of the moons were too close together, during subsequent nights, until January 13, when he was able to see all four for the first time.
Wikipedia is wrong on one point. True, his first observation of all four moon at once didn't come until January 13 and he didn't realize that there were four and not three until that time, but that doesn't mean that one moon's discovery (in Wikipedia's case, Ganymede) should be attributed to that date. By that point, he had observed all four on multiple occasions, just not all four at once. And to that point he hadn't even come to the conclusion that they were in orbit around Jupiter with their own separate orbits, moving a different speeds, until two days later, let alone ascribe identities to each of the stars he saw, connecting one star he saw with another from a different day, beyond the one to the east, the one to the west, and the one in the middle.
The Gish Bar Times - Blog covering Jupiter's moon Io
Wow, somebody else is pointing out other things that got left out when people talk about the Saint of Science. On top of what you've added the church actually updated their position to the Tychonic model. (Where the Sun and Moon orbit the Earth and the planets orbit the Sun.) The big problem with the Earth going around the Sun is the stars should exibit parallax. There's a few explainations for this. One is the Earth moves but the stars are so far away that they couldn't measure it. The other is it's not actually there because the Earth doesn't move. Tycho's system had the Earth not moving which was a valid point of view given the evidence. (Of course in the 1800's they could finally see the parallax and they knew the Earth moved. Well actually they knew about it before then because Newtonian mechanics pretty much require the Earth to move but they didn't have that either when G was kicking around.) Anyway like you say, if you play around with politics at that time period it could work out badly. (Because that's how politics were at that time.)
Did you know 80 to 90% of the moderators on slashdot wouldn't recognize a troll even if one dragged them under a bridge.
When does it snow on Titan? Rain, yes. Lots of Rain, sure. A gentle drizzle from the stratosphere, why not? But, nope, no snow... not cold enough for methane or ethane to fall as snow on Titan, even at the winter pole.
The Gish Bar Times - Blog covering Jupiter's moon Io
The Italian city-states of the time weren't terribly friendly to non-conformists, actually. Galileo got off lucky. Violation of sumptuary laws, i.e. wearing clothes that were above your station (there was a hierarchy of rankings, and only the Doge himself could wear Cloth-of-Gold), resulted in the offender being found the next morning buried upside down in a shallow pond, head deep, with their legs tied to a pole (sort of like a Hipgnosis album cover). A conformist society, that, but inventive in a way that wasn't to be matched until the development of formal defenestration by Russia in the 19th century. If you wanted security it helped to have patronage, though that required you to make moral compromises at times (such as DaVinci touring around Florence with Cesare Borgia, documenting plant poisons around 1510-ish). From all this, I suspect Galileo was taking a stand on more than scientific principles (or was dreadfully naiive, perhaps).
Do not mock my vision of impractical footwear
Copernicus had proposed a heliocentric system almost a century before Galileo, and yet suffered no persecution by the Church because of it.
Ah, but this is only because Copernicus, a devoute Catholic, feared and respected the Church, recognized that his theories (which actually others had suggested before, though none would take credit (blame) for them) would be disruptive, and cleverly published his theories posthumously. Had he been alive, the Church surely would have killed him.
The Admin and the Engineer