The precession of Earth's axis, also called "luni-solar precession", is one of the most important motions of the Earth, where the axis of rotation does not always point in the same direction in space.
If we look at the layout of the Earth during a revolution of the planet around the Sun, we see that the rotational axis remains always parallel to itself. In fact, the Earth's axis does not change its angle to the orbital plane, but the orientation.
The axis of the Earth, and consequently the celestial axis, pivoting in the center of the globe makes a full cycle in 25,765 years, thus mapping two symmetrical cones. The Precession is mainly due to the Moon (turning around the Earth moves the axis direction) and the equatorial bulge, making the Earth turn like a spinning top -- even the gravitational force of the Sun and planets affects the precession motion, but to a lesser extent.
As a result of the precession movement very slowly change the visibility of all constellations in the sky, over the centuries. We know that Polaris, the North Star, is currently the Alpha Star of the Constellation Ursa Minor (also called Little Dipper or Little Bear). In 2,000 years, the North Star will be Gamma Cephei, then Beta Cephei and Alpha Cephei, which are stars in the Constellation Cepheus. In about 10,000 years, the North Star will be the Delta Star in the Constellation Cygnus, in another 5,000 years the Iota Star in the Constellation Hercules -- of course, other stars will take the place of Polaris in the northern sky, as Vega and Deneb.
When the Earth's axis completes the precessional cycle, in about 26,000 years, the North Star will be Polaris again. In fact, for each full cycle the pole star never goes in the same position, because our sun and other stars move through space in different directions and speeds (no one mentions this).
Moreover, because of the precession movement, all the constellations that are currently visible in the Northern Hemisphere, will be visible in the Southern Hemisphere at mid-cycle of rotational axis, and vice versa. An imaginary observer located at a fixed point of the outer Solar System (it could be the orbit of Mars) every 13,000 years will see that the seasons are reversed on Earth, first right of the Sun then left. But we don't realize it, because the movement of the Earth's axis is imperceptible, only an angle of 0.014 degrees per year! Exactly the difference between solar year and sidereal year (0° 0' 50.4'').
Note : The precession of the Equinoxes does not exactly match the precession of Earth's axis, because it's a combination of the axial precession and the precession of the apsides (aphelion and perihelion shift over time around the Sun). This implies that the reversal of seasons takes place in advance, approximately every 10,500 years, not every 13,000 years as in the above theory.
I hope my explanation has been sufficiently understandable. Thanks so much for reading!
This three-dimensional graphics was made for the Planetarium of Milan in Italy.
Website: [ Ссылка ]
Images of Earth/Moon taken by distant spacecrafts July 19, 2013:
[ Ссылка ]
Planet X (Nibiru) is a Hoax, and Speculation:
[ Ссылка ]
Ref to Thomas Gron's Comment :
In an old comment below, I specified the zodiac signs are assigned to months and they are indicative only -- non-functional in the precession cycle of 26,000 years, just because it's impossible to build it in a 3D graphics animation of 90 seconds -- but he probably did not read anything.
I think he does not have very clear ideas about the precession, and how the universe really works.
With reference to the operation of the mirror telescopes, he has written only nonsense.
Maybe, he needs to learn / understand better the Astronomical Sciences!
