On Sep 21, 8:30*am, Martin Brown
wrote:
On 21/09/2012 02:32, RichD wrote:

When and how did astronomers determine that the earth's axis
tilts from the ecliptic, and its value?

A reasonable list of who, what, when and where is online at:

http://articles.adsabs.harvard.edu/c..._query?1979A%2...


Regards,
Martin Brown

Years ago you could get away with that stuff but not in front of a
genuine astronomer.

In antiquity they used a shadow at the Solstice to determine the
circumference of the Earth,something quite different than daily
orientation.so your referenced paper is not only a non starter,it has
all the usual empirical pretension and none of the substance.The same
with the Galileo affair,the technical issues as the Pope understood
them was far more involved and with greater depth than shown by any of
contemporaries and I wouldn't even entertain a discussion here among
those for whom magnification constitutes astronomy and a few
mathematicians pretending to know something.

For a more comprehensive and accurate,do you hear this Brown, an
accurate use of a shadow at the solstice,there are only a very few
accurate perspectives and Stecchini,apart from his few quirks,happens
to be one of them -

"Eratosthenes was not the first to measure the circumference of the
Earth, but the first to argue, contrary to the opinion of Aristotle,
that the calculations about the circumference of the Earth could be
accepted as proven in terms of the new scientific style.

A series of ancient authors credits Eratosthenes as having introduced
the calculation of the degree as equal to 700 stadia, but there is not
a single writer who indicates that he based himself on an empirical
survey of the ground. Contemporary scholars exalt Eratosthenes as a
great scientist and as a pioneer in mathematical geography, but none
of the ancient writers who were acquainted with his works indicate
this. If Eratosthenes had been such an innovator, Ptolemy who
discusses at length the problem of the dimensions of the Earth in the
Prolegomena to his Geography would have said at least some words to
this effect. Theon of Smyrna and Proklos, who lived in Alexandria do
not make any reference to the alleged discovery of Eratosthenes in
their extensive commentaries on ancient mathematical science. Strabo,
who had before his eyes the writings of Eratosthenes and discusses
them at length, does not ascribe to Eratosthenes any specific
achievement in the field of empirical geodesy or of theoretical
geography. Strabo mentions repeatedly the figure of 700 stadia to the
degree, but justifies it only in these words: “We suppose as
Hipparchos, that the size of the Earth is 252,000 stadia, a figure
given also by Eratosthenes.” He would not have spoken in these terms
if Eratosthenes had provided a complete mathematical demonstration."

http://www.metrum.org/measures/measurements.htm

The next time you post some reference that you pull out of thin air,be
sure to know what you are talking about first both historically and
technicallyy.