Caption: The axial precession of Earth's rotation axis is due to the tidal force on Earth of the gravity of the Moon, the Sun, and, to a much lesser degree, the planets.
The tidal force acts primarily on the Earth's rotational bulge. It tries to torque the Earth's axis into approximate alignment with the ecliptic axis. However, since the Earth is rotating on its axis, the torque has the result of causing the axial precession.
Rotational effects like axial precession defy simple explanation.
But they are fairly common. A spinning toy top exhibits precession.
Credit/Permission: NASA,
2008
(uploaded to Wikipedia
by User:Mysid,
2008) /
Public domain.
Image link: Wikipedia:
File:Earth precession.svg.
Local file: local link: axial_precession.html.
File: Celestial sphere file:
axial_precession.html.
