Slow Turning

The Earth seems to be slowing down:

Part of the trouble is that Earth’s deep interior is impossible to observe or sample directly. Seismologists have gleaned information about the inner core’s motion by examining how waves from large earthquakes that ping this area behave. Variations between waves of similar strengths that passed through the core at different times enabled scientists to measure changes in the inner core’s position and calculate its spin. “Differential rotation of the inner core was proposed as a phenomenon in the 1970s and ’80s, but it wasn’t until the ‘90s that seismological evidence was published,” said Dr. Lauren Waszek, a senior lecturer of physical sciences at James Cook University in Australia. But researchers argued over how to interpret these findings, “primarily due to the challenge of making detailed observations of the inner core, due to its remoteness and limited available data,” Waszek said. As a result, “studies which followed over the next years and decades disagree on the rate of rotation, and also its direction with respect to the mantle,” she added. Some analyses even proposed that the core didn’t rotate at all.

The world spins with or without us...