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From: sho2@chat.carleton.ca (Sam Ho)
Subject: Re: Heliocentricism (Re: THE PURPOSE OF LIFE Defined & Gaia)
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References: <3d0eciINNm84@ringer.syd.dwt.CSIRO.AU> <3ek7mk$l86@ixnews3.ix.netcom.com> <ONEAL.95Jan19201224@trantor.astro.psu.edu>
Date: Tue, 24 Jan 1995 02:09:42 GMT
Lines: 93


g
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Doug O'Neal (oneal@astro.psu.edu) wrote:
> In article <19JAN95.13317188.0017@ESAMATC.LIB.MATC.EDU> Raven <JSINGLE@MUSIC.LIB.MATC.EDU> writes:
> >   Sharon Steiner <sharon@best.com> wrote:
> >  |>The actual dichotomy was whether the earth was fixed or moving. Was it not
> >  |>Galileo who first postulated that the earth was not the center of the
> >  |>universe but rather circled the sun? IMO this was the time when the concept
> >  |>was not accepted by the scientific community. He was required to recant his
> >  |>statement.

> >  Andrzej Pindor <pindor@gpu.utcc.utoronto.ca> pointed out:
> >  |Actually, it was Copernicus who first proposed the idea. Galileo was actively
> >  |promoting Copernicus' idea and ran afoul of Inquisition.

> >   It should also be pointed out that the concept was "not accepted by" the
> >  CHURCH, which is and was a set distinct from "the scientific community".

>  (DELURK)  There's a lot of interesting history behind this; for an overview, 
>  read just about anything by astronomer/science historian Owen Gingerich. 

>  Copernicus was indeed the first person in modern times to propose the 
>  heliocentric theory.  There's some evidence that the Greek Aristarchus may 
>  have considered the idea though; in Copernicus' book he writes, "Aristarchus 
>  of Samos may have been of this opinion".  That possibility comes from a brief 
>  phrase in the writings of a later Greek scientist (Hipparchos?).  

>  However, astronomy in the time of Copernicus was very different in 
>  philosophy than the astrophysics of today.  Then, astronomy was chiefly 
>  concerned with computing accurate tables and formulae that would allow 
>  one to predict where in the sky a given planet would appear at a given 
>  time.  The idea that astronomical models corresponded to actual reality -- 
>  the philosophy that drives astronomy nowadays -- didn't exist back then. 
>  Copernicus himself believed that his heliocentric system was only another 
>  idea, a possibility, a concept for making the calculations easier.  In fact, 
>  his tables weren't much more accurate than those of Ptolemy. 

>  The scientific community wasn't immediately convinced.  Half a century after 
>  Copernicus, Tycho Brahe (he of the gold nose) proposed his own hybrid 
>  system, in which the Sun weent around the Earth but everything else went 
>  around the Sun.  Tycho's very careful observations of planetary positions 
>  made it possible for Kepler to derive his very heliocentric laws of 
>  planetary motion; Kepler did consider his ideas as physical reality, and 
>  in fact (this was 80 years before Newton's gravitation) postulated a magnetic 
>  force in the Sun that drove the planets in their orbits. 

>  Galileo did provide the observations that made the heliocentric universe 
>  more likely.  The clincher (in his mind) was that Venus shows phases like 
>  those of the moon.  In a geocentric cosmology, Venus would always appear 
>  as a crescent, never as gibbous or full.  Galileo's reasoning, however, 
>  was something that the learned world wasn't used to: backwards logic, the 
>  kind that most science relies on today.  Consider the statement: "If the 
>  solar system is heliocentric, Venus will show moon-like phases".  Galileo 
>  observed that Venus shows moon-like phases; therefore, the solar system is 
>  heliocentric.  It's this kind of model building and relying on likelihoods 
>  on which modern science depends; but it was new in his day, and in fact, 
>  as a syllogism, it's backwards.  Thus theologians and others were still 
>  able to claim, well, there could be another reason for Venus to show 
>  complete phases.  

>  In about 1616, the liberal Urban the something was elected pope, so 
>  Galileo was optimistic that he'd be able to freely present his idea.  In 
>  fact, he made an agreement with the church that he'd write a book that 
>  neutrally examined the geocentric vs. heliocentric possibilities.  What 
>  he produced was "A Dialogue Concerning the Two Great World Systems"; it was 
>  anything but a neutral discussion.  The character advocating the old 
>  geocentric idea -- the pope's idea -- was named Simplicio.  Bad move.  
>  It was clear what the author's stance was.  That's what got Galileo into 
>  trouble. 

>  As a result of Galileo's persecution, the center of science activity 
>  moved northward to the protestant countries, and by the end of the 
>  seventeenth century, after the work of Halley and Newton, Descartes, and 
>  others, heliocentricism was irreversibly ingrained in the world view 
>  of scientists and philosophers.  

> >   -- Raven (JSingle@Music.Lib.MATC.Edu).  [All standard disclaimers apply]

> 	Reporting live from Kitt Peak, Arizona 


> 								Doug 



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Sam Ho
Carleton University

Email address: sho2@chat.carleton.ca
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