Subject: Re: [HM] Aristarchus
From: Rene Grognard (Rene.Grognard@tip.csiro.au)
Date: Thu Feb 10 2000 - 19:43:46 EST
A few comments if I may:
> Kim Plofker wrote:
> I think, the complex geocentric system of Ptolemy is a much more
> remarkable accomplishment than the heliocentric speculations of
> Aristarchus.
>
> and Al Barron wrote
>
> Now that's curious opinion. Is this a prevailing view among historians
> of mathematics ?
>
The late Otto Neugebauer's monumental work on the "History of Ancient
Mathematical Astronomy" gives to Ptolemy's theory the important place it
rightly deserves.
However amongst astronomers it is the fashion to disparage Ptolemy's work
(some even calling him a "fraud") and to mention Aristarchus only as one
that _might_ have influenced Copernicus, surely through Archimedes'
statement in the Sand Reckoner since there is no other source. (By the way
why would any basis to doubt Archimedes' word on that point be judged
itself any more reliable ?)
The only serious exception that I know is Sir Fred Hoyle's popular book on
"Astronomy", Macdonald: London, 1962.
In particular Hoyle presents an "Appendix on the Epicyclic Constructions of
Hipparchus and Ptolemy" (pp 306-309), where he makes use of complex
analysis to bring forth, in a condensed manner, "the subtlety of Ptolemy".
In a lecture he gave many years ago in our Radiophysics laboratory (then
dedicated to radioastronomy) he even compared Ptolemy's method to the
Fourier analysis of tides and other periodic or quasi-periodic observational
data sets.
Another comment on possible sources of Greek astronomy in Egypt.
I don't think that even Herodotus could have made such a claim. Again a
long association with Egyptologists (and study of the classical Middle
Kingdom language -- for fun) at the nearby Macquarie University gave me no
ground to doubt the assessment of Otto Neugebauer and Richard Parker
("Egyptian Astronomical Texts") . Egyptian astronomy was far too primitive
to serve as basis to Greek astronomy.
For instance the most elaborate "relics" of Egyptian astronomy: the
Egyptian Star clock systems (using decans in rising as on the early coffin
lids or in transit as in Ramesside period) were unworkable because simply
based on the civil year of 36 x 10 days + 5 epagomenoi (in Egyptian: "the
ones [left] over"). Indeed there were endlessly corrected with the result
of a bewildering confusion of surviving evidence painstakingly sifted by
Neugebauer & Parker. In fact it might very well be argued that water clocks
were finally adopted simply as a more practical device to measure time.
There is no text indicating any Egyptian interest in the complexity of
celestial motions, exception made for the 70 day period of invisibility
between the acronychal (=at dusk) setting and the heliacal rising of
Sirius (and the decanal stars) : period "spent" in the Underworld ("dwt")
between their "death" and "rising". This period was adopted for the
canonical duration of embalment.
R J-M Grognard.
This archive was generated by hypermail 2b28 : Thu Feb 10 2000 - 19:54:06 EST