CANBERRA - The center of the Earth is out of sync with the rest of the planet, frequently speeding up and slowing down, a new study from the Australian National University (ANU) found on Monday.

The research is published Monday in Nature Geoscience. The research team from the ANU College of Physical and Mathematical Sciences led by Associate Professor Hrvoje Tkalcic used earthquake doublets to measure the rotation speed of Earth's inner core over the last 50 years.

They found that the inner core not only rotates at a different rate to the mantle, ?the layer between the core and the crust that makes up most of the planet's interior, ?its rotation speed was also variable.

This is the first experimental evidence that the inner core has rotated at a variety of different speeds, Professor Tkalcic said.

"We found that, compared with the mantle, the inner core was rotating more quickly in the 1970s and 1990s, but slowed down in the 80s. The most dramatic acceleration has possibly occurred in the last few years, although further tests are needed to confirm that observation," he said in a statement.

"Interestingly, Edmund Halley, namesake of Halley's Comet, speculated that the inner shells of the Earth rotate with a different speed back in 1692." He added. And Tkalcic said this new method could help us understand the role of the inner core in creating the magnetic field that allowed life to evolve on Earth by acting as a shield from cosmic radiation.