If the polar axis of Earth moves through a full circle in 26,000 years as a result of precession (see Figure 1-19c,Comins,Discovering the Essential Universe,6th ed.),how long will it take for the line between the center of the circle and the spin axis to move through 180° (i.e.,to the other side of the circle)?
A) 26,000 years
B) 1 year
C) about 100 years
D) 13,000 years

Question

Quizplus · Accepted Answer

Since the polar axis moves through a full circle in 26,000 years, it will move through half a circle (180°) in half that time, which is 13,000 years. Therefore, the answer is D) 13,000 years.

If the Polar Axis of Earth Moves Through a Full