This is where from the very top point of the earth, an exact circle has been rotated around on the earths axis and this takes 25,765 years purely because it is an astronomical feat. The earth orbits inside and outside the circle but is never generally on track with the circle making an estimate hard to find out on when it last occurred and for how long but a close estimate has been assumed as told above.
Precession has been recorded and noted down a few times in history, with the ancient Egyptians for example. During precession planets can align themselves exactly in front of each other to create an eclipse. This was considered an unholy rage from the gos by the Egyptians as they could not comprehend why the sky had suddenly turned black. After this across the world races and cultures started creating pyres, effigy's, temples and so on as to appease the sun god in hope that an eclipse would never happen again, fortunately for them there would not be another eclipse unless they can live for 25,765 years.
There has also been a previous debate as to a Mayan prediction that the planet will line up with the galactic plane on 2012. This is a known fact that will happen, nd scientists do not know how the Mayan people could have predicted this so accuratley without equipment. The debate is to what will happen when the planet lines up with the galactic plane. Religion has been completely ruled out of this topic as it would have caused far too much meaningless debate but scientists are indefinite as to what will happen during the allignment. Some theories include, ice age, ultraviolet planetary obliteration, black holes, unstable dark matter. Currently you can read up on a subject i have wrote on dark matter aka space dust to get some insight as to what this is.
