"Davoud" wrote in message ...
RichD:
When and how did astronomers determine that the earth's axis
tilts from the ecliptic, and its value?

Bast:
I guess the answer depends on who you ask.

Indeed, it does. My dad was first a ship's navigator and then a pilot
in his young years. It was he who first told me about the stars. I
remember him asking me when I was not very far along in elementary
school "Have they taught you yet that Columbus proved that the Earth is
round?" "No? Well, they will. Don't make a fuss over it, but they're
wrong. Eratosthenes, who lived hundreds of years B.C., knew the Earth
was round and he even made an accurate measurement of its
circumference. So educated men have known for more than 2,000 years
that the Earth is round."

I didn't make a fuss over it when the time came in geography class, but
I did tell the teacher to check out Eratosthenes in the encyclopedia.
(That was a set of about 30 books printed on paper in those days.)

I don't have time to do the searching at the moment, but I have to
think that ancient natural philosophers, whether in Greece or Persia or
China or parts unknown, knew the extent of the Earth's axial tilt. Just
about anyone who gave it some thought could figure it out, even if they
believed in a geocentric Universe. Otherwise they would have to think
that the Universe wobbled as it orbited the Earth. That could be
accounted for, but there were people who were smarter than that.


-

Not only did educated men know, but they also had built a computer
to model it.
http://en.wikipedia.org/wiki/Antikythera_mechanism

Ancient Greek technology was destroyed by Roman barbarians and not
duplicated until Victorian England, long after Galileo Galilei challenged
the Roman Barbarian Church.

- This message is brought to you from the keyboard of
Lord Androcles, Zeroth Earl of Medway