An 8.5-year-long wobble means Earth's core and mantle are not aligned

Scientists have made an 'essential' discovery that can help us understand the Earth's structure.

Researchers from China have been looking into the Earth's inner core and confirmed that it has a wobbling motion that repeats over a set period of time.

They've imaginatively dubbed this the Inner Core Wobble (ICW), and found that it affects the motion of the Earth's poles, as well as length-of-day variations.

The ICW is characterized by a periodic oscillation of the inner core's figure axis.

It's now been revealed that the inner core is off around 0.17 degrees compared to the mantle - which is drastically different to previous assumptions that it was 10 degrees, suggesting a more complex relationship between the different layers of the Earth than previously understood.

To identify the ICW, the team analyzed Earth’s polar motion and variations in the length of a day.

They had to rule out other things like atmospheric, oceanic, or hydrological factors in the process.

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For those of you (like me) who aren't terribly science minded, the inner core is the very center of our planet and is made up of almost entirely metal.

Around the inner core is, you guessed it, the outer core, which is made up of molten liquid metal.

The mantle then sits on top of the outer core.

As well as confirming that the ICW exists, researchers say that it has a predictable rhythm that repeats every 8.5 years.

This is a big deal because the Earth's structure plays a part in what happens to us on its surface - the length of the days, for example.

Professor Hao Ding, co-author of this research and Dean of the Geophysics Department at Wuhan University, told Phys.org: "Results of the Earth's free oscillation (natural oscillations of Earth as a whole) indicate that the density structures of the Earth's interior are highly heterogeneous."

Dr. Ding/Nature Communications

As to why this discovery is so important, the new findings have raised questions about what scientists thought they knew before about the Earth’s geophysical processes.

Professor Ding went on: "These deviations offer valuable constraints for the 3D density model of the mantle and question assumptions in the liquidity-core oblate, highlighting potential deviations from a perfectly spherical form calculated using traditional theories."

Their findings come after seismologists at the Australian National University recently found the 'innermost inner core' of the Earth.

This is said to be slightly different to the rest of the inner core, and was in fact a giant metal ball about 400 miles wide.