What is precession and What are some of its possible consequences?

Answer 1

Precession is the slow wobble of the Earth due to the fact that the Earth is not perfectly round and therefore the Sun and the Moon's gravitational pull is somewhat stronger on the equator of the Earth than elsewhere. A "torque" like this will cause any rotating object to wobble. The period of one complete precesssion cycle is almost 26,000 years.

A consequences of the precession cycle is that the position on the Earth's orbit around the Sun where winter (in the North) is now will be where summer occurs in 13,000 years. This slow drift of the seasons prompted the Catholic church to call for the implementation of a new calendar called the Gregorian calendar which accounts for precession.

Answer 2

'Precession' might be described as 'axial wobbling'.

If we think of the Earth's North and South Poles, they lie on a line directly through the centre of the Earth. This line is angled at 23.5 degrees to the orbital plane. As a result it gives us the seasons.

However, this line that is tilted at 23.5 degrees is NOT a static angle, but varies over thousands of years. Currently it is decreasing , and will eventually reach an angle of approximately 20 degrees (the seasons will be less extreme). Whereupon, it will then start to increase again to about 30 degrees (the seasons will become more extreme) .

This tilting movement is called precession.

As an experiment, if you have a child's spinning top or a gyro, set it spinning. You will notice that it 'wobbles', this is precession. The Earth does exactly the same, over thousands of years.