----- Original Message -----
Sent: Friday, February 20, 2004 10:42
AM
Subject: Retrograde motion Re: Birthday
Challenge
The retrograde motion of the planets (Mars in particular) is something
that it very easy to observe. In fact, the ancients certainly were much
more familiar with the heavens than we are. They had more time at night
and were outside more. They didn't have light pollution to deal with, or
television and inside lighting to keep them from looking up regularly.
Retrograde motion cannot really be explained with a geocentric
model. It was attempted and even believed, but the theories were
far-fetched. (Easy to say with hindsight! :o)
I'm lucky enough to live in a rural setting (15 miles to the nearest
town, and it's not very big or bright), so I get to see the Milky Way
regularly in the Fall and Winter. Without meaning to, I keep track
of the motions of the planets in relation to the celestial sphere, etc.
If someone in ancient times were serious academically about studying the
issue, the retrograde motion was a big factor, I think.
Does anyone know who first proposed a heliocentric solar system?
Albert Franco
[EMAIL PROTECTED] wrote:
In einer eMail vom 20.2.2004 03:42:38 Westeuropäische
Normalzeit schreibt [EMAIL PROTECTED]:
Weeeellll, the Foucalt Pendulum would prove that the Earth
rotates, but I
don't think it gives any evidence that it revolves about
the Sun. What
could we do to take it a step
further?
It does in principle, but it would be hard
to get the accuracy. Other things, like parallax and astronomical
aberration, are also impossible to measure with 15th-17th century
technology. But I'm sure once you convinced people with a Foucault
pendulum that the Earth moved *at all*, it would be only a small step from
accepting rotation to accepting revolution.
Art Carlson
P.S. I
can't leave that loaded pun lying around where children might play with
it: The revolution was the rotation. Once that was accepted, the
revolution (of the Earth around the sun) was no longer a revolution (in
world view).
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