See any of the following on Aristarchus. http://www.perseus.tufts.edu/GreekScience/Students/Kristen/Aristarchus.html http://www.astro.utoronto.ca/~seaquist/sci199y/presentations/pye_1.html http://csep10.phys.utk.edu/astr161/lect/retrograde/copernican.html
----- Original Message ----- From: "Albert Franco" <[EMAIL PROTECTED]> To: <sundial@rrz.uni-koeln.de> Sent: Saturday, February 21, 2004 9:33 AM Subject: Re: Birthday Challenge > That was my point when I put that the geocentric explanations for > retrograde motion aren't very convincing. (I don't recall my exact > words.) Dr. Carlson hits the nail on the head with the term "DESCRIBED > in the frame of reference of the Earth." > > I feel the descriptions of retrograde motion in geocentric models are > just that . . . descriptions from a frame of reference. They are > counter-intuitive and don't make much sense in reality. It is hard to > imagine why a planet would be making an orbit and suddenly make a > smaller loop. > > ** What was it that made Aristarchus, in 250 BC, decide upon a > heliocentric model with Earth orbiting and revolving? I've read > textbooks in which Aristarchus was very quickly mentioned, but I don't > know much about the man or his theory. (Which is why I didn't recall > his name or exactly when he lived.) > > Another naked eye observation I thought of was lunar eclipses and solar > eclipses. Eclipses just don't add up properly without a heliocentric > model. I am aware that people in modern times have put forth other > explanations (hopefully to show that science isn't 100% and must always > be questioned), but some things, as Dr. Carlson says, are merely > descriptions from a chosen reference, and not in touch with reality. A > prime example is the equatorial coordinate system vs. the altazimuth > coordinate system. The latter is much easier to use, and can be used > easiest by thinking of the Sun, Moon, stars and planets as rotating > about the Earth and crossing the sky. It is a geocentric model > basically, and we are on Earth, so our minds are geocentrically > centered. It is a way to describe the motions of heavenly bodies "in > the frame of reference of the Earth." > > I remember reading a story (Assimov?) about a Long Night. That may > have been the title. Supposedly the eclipse that came at the end of > the story lasted for hundreds of years. I didn't feel it was > believeable, however, because the eclipse came on rather quickly. It > seems that the prenumbra/umbra situation would require a gradual > darkening for such a lengthy eclipse. And, the moon would travel very > slowly or be huge so watching it begin to eclipse the sun would not be > a matter of a few hours. > > Does anyone remember the short story's title or author? I'll look it > up if no one does, to give credit. I'm sure I have it somewhere. > > Albert Franco > [EMAIL PROTECTED] > > > > > --- [EMAIL PROTECTED] wrote: > > Hello, Roger, > If you are looking for a purely > > kinematic proof, > > like sundials and records of planetary motion, then it is a > > mathematical > > triviality that the motion of everything can be described in the > > frame of reference of > > the Earth. > > > > Cheers, > > > > Art > > > > > __________________________________ > Do you Yahoo!? > Yahoo! Mail SpamGuard - Read only the mail you want. > http://antispam.yahoo.com/tools > - -
