Saturday, April 18, 2015
P is for precession #atozchallenge
What is precession?
The Earth revolves on its axis once every 24 hours which forms our day. However, the Earth's axis is not a fixed point in space. The axis wobbles like a gyroscope or a child's toy top. Therefore, it points to a different set of stars. The period of precession is 26,000 years. Precession is the result of the Moon's and the Sun's gravitational pull on the Earth.
The Pole Star is the northern hemisphere is Polaris in 2015 A.D. In 3000 B.C., the Pole Star was Thuban in the constellation of Draco. In 14,000 A.D., the Pole Star will be Vega in the constellation of Lyra.