Astronomers have long known that the Earth wobbles as it spins. Several irregularities in rotation—small oscillations superimposed upon larger wobbles atop even larger waggles—cause the location of the true North Pole, about which the Earth rotates, to meander across the Arctic landscape.
The causes of some components of the pole's overall movement are well understood, but the driving force for one element—the so-called Chandler wobble—has remained a mystery.
Seth Carlos Chandler Jr., a businessman turned astronomer, discovered this phenomenon in 1891. By itself, the Chandler wobble would cause the pole to move back and forth about 20 feet every 14 months. Scientists have calculated that the wobble would die out within 68 years if there weren't a constant source of energy to reinvigorate it.
Over the past century, some researchers suggested that interactions between Earth's core and the mantle that surrounds it cause the wobble. Others bla