Re: question about inclination of earth's axis.

On 24 May 2006 10:10:21 -0700, obhiee@xxxxxxxxxxx wrote:

I'm curious. Suppose I were to be deprived of technology and had to
rely only upon my observation, and intuition, how would I know that
Earth's axis is inclined at an angle instead of being perpendicular?

How did the ancients know that the axis of Earth is not perpendicular,
but inclined ?

By looking at the apparent path of the Sun in the sky. The sun is
high at noon in Summer, low at noon in Winter and midway during the
Spring and Autumn. It is just as if the orbit of the Sun was in a
plane inclined at 23-1/2 degrees to the plane of the Earth's equator
(in the geocentric planetary systems of the day).

Dreyer's History of Astronomy from Thales to Kepler has good coverage
of Greek astronomy.
.

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