Final answer:
The Earth's axis undergoes a slow tipping motion in a circular pattern known as precession, which takes approximately 26,000 years to complete and is primarily caused by gravitational forces from the Moon and Sun.
Step-by-step explanation:
The slow tipping of the Earth's axis in a circle with a period of about 26,000 years is called precession. This motion is analogous to a spinning top, which wobbles as it slows down. Precession is primarily caused by the gravitational pull from the Moon and Sun on Earth's equatorial bulge.
This gravitational nudging results in Earth's axis tracing a conical shape in space. The precessional cycle not only alters the direction in which the Earth's axis points but also has implications for the timing of the seasons, as it changes the point during the year when the northern hemisphere is tilted towards the Sun. Presently, Polaris is our north star due to precession, but thousands of years ago, it was Thuban, and in the future, it will be Vega.