Abhishek 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 ?

The axis of the Earth is clearly not perpendicular to the ecliptic (the
apparent orbital plane of the sun), because if it were, we wouldn't have
any seasons. The Sun would always cross the sky at the same height, day
after day.

The amazing thing to me is that the Greeks even uncovered the precession
of the equinoxes, and even gave a decent estimate as to how long the
period is--about 36,000 years. (The actual value is about 25,800.)

--
Brian Tung
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