On Thursday 26 May 2011, Levi Pearson wrote: > On Thu, May 26, 2011 at 12:06 PM, Daniel C. <[email protected]> wrote: > > So if I lived in Greece in the 4th century BC, then the Sun I saw > > rising each day was stationary and the Earth revolved around it; > > unless I was a Pythagorean, in which case the Earth revolved around > > the Sun; but if I left Greece and moved to Egypt, it goes back to the > > Earth being stationary (in Egypt, at least), until I can convince > > everyone that they're wrong and I'm right and once that happens the > > Sun stops moving and the Earth starts up again. > > > > All of this is of course perfectly sensible and could not under any > > circumstances be challenged except by the most intellectually obtuse, > > but I'm still confused about something. Hopefully you can enlighten > > me. We know that in Egypt in the 4th century BC the Sun revolved > > around the Earth, since that's what everyone believed. But when half > > of the people in Egypt believe that the Earth is stationary, and half > > of the people in Egypt believe that the Sun is stationary, which one > > is moving and which one is holding still? The answer is probably > > obvious, but I'm just too dumb to see it. Can you help me out, Alan? > > It is indeed true that the sun moves around the Earth, even today. > It's just that when you consider solar and planetary motion from an > Earth-centric frame of reference, it's much more difficult to model > and predict the paths of bodies, and it doesn't reflect the actual > forces that constrain the paths.
If I recall the history correctly, Copernicus made the mistake of assuming the orbit of the planets had to be circles instead of ellipses, thus necessitating the need to add epicycles to his heliocentric model, similar to the geocentric model. This made the heliocentric model just as complicated as the geocentric model, so there was really no big push to go to to a new model when the old one was just as good. Although, the heliocentric model did explain observations such as the phases of Venus. /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
