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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Universe of the ancient Greeks.
From: Frank Reed CT
Date: 2006 Mar 14, 02:12 EST
From: Frank Reed CT
Date: 2006 Mar 14, 02:12 EST
Lu Abel, you wrote: "While I hesitate to disagree with such giants of this list as George Huxtable and Frank Reed..." Ho ho ho. For the record, I am 5 foot 8, quite ungigantic, and an amateur in these matters, just like everyone else on this list. And then you asked: "what about the motion of the planets?" What about 'em?? It is a popular myth that the Copernican system was significantly simpler than the Ptolemaic. Most of "de Revolutionibus" is actually about epicycles. There's some of this that's worth reading in a book I mentioned recently "The Book Nobody Read" by Owen Gingerich. He has a section on the popular misconception that the Ptolemaic system was slowly weighed down by "epicycles upon epicycles". And: "If earth and the planets all were in circular orbits around the Sun, the apparent motion of the planets was easily explained by their relative motion with respect to the earth." EARTH and the planets... We say it so easily today. The Earth is a planet, of course, why didn't we think of that earlier? In fact, it was the first planet discovered by science. The others had been seen since the dawn of history. But it's not obvious at all until you invent the telescope. So here's Copernicus, pre-telescope, and he's got an explanation for the Solar System. It's one that is certainly not more complicated than the Ptolemaic, and it produces predicted positions that are just as good (but still pretty bad in many cases). An equivalent model producing equivalent data starting from radically different assumptions... That's the sort of thing that launches a revolution. -FER 42.0N 87.7W, or 41.4N 72.1W. www.HistoricalAtlas.com/lunars